Genetics and human behavior. The influence of genetic inheritance on behavior. The influence of heredity on alcohol abuse

Genetic studies of behavior have significant implications for a number of areas of biology and medicine. Firstly, they must be the basis on which only certain areas of the physiology of higher nervous activity can develop. The study of individual differences in higher nervous activity (including the study of its types) and the elucidation of the relative role of innate and individually acquired components of behavior are impossible without genetic analysis.

Fully understanding this, I.P. Pavlov created a laboratory in Koltushi for the genetics of higher nervous activity.

Secondly, genetics makes it possible, with the help of crosses, to separate and combine in hybrid offspring these and other behavioral features with various morphophysiological properties of the organism and to clarify the correlations between both. This opens up a new, subtle method for studying the dependence of behavior formation on the morphophysiological properties of the organism, which is impossible using modern surgical or physiological methods.

Thirdly, the study of the genetics of behavior is of great importance for a number of problems of evolutionary theory. Genetically determined behavioral characteristics of animals play a role in the structure of populations. Hereditary differences in behavior determine the formation of isolated populations of different sizes, which is of great importance for the pace of the evolutionary process.

Fourthly, the study of the genetics of animal behavior is important for finding new methods for the most rational domestication of economically useful animals. This is of especially great practical importance for fur and livestock farms.

Fifth, behavioral genetics is necessary to create experimental models of nervous diseases. Several dozen neurological hereditary diseases have been described in mice and are being studied as experimental models of human diseases. The genotypically determined model of epilepsy is widely studied in rodents in all countries. In 1965, an international colloquium in France was devoted to this issue.

Genetic studies of behavioral patterns began shortly after the secondary discovery of Mendel's laws. The material accumulated to date shows that many behavioral characteristics are inherited according to Mendel's laws, but in most cases a number of factors change the pattern of their inheritance.

For genetic studies of behavior, defensive reactions in animals have proven to be a convenient model. A number of studies have been devoted to this issue.

Rice. 1. Inheritance of fearfulness in mice

In 1932, Dawson conducted research into the mode of inheritance of pronounced timidity in wild mice compared with the weak expression of this trait in laboratory mice. A total of 3,376 individuals were studied. An objective recording method was used: the time spent running down a 24-foot corridor while being startled by a moving mouse. A preliminary study revealed a high correlation (r=+0.92+0.003) between individual trials of the same mice, indicating significant stability in the behavioral traits studied. The average running time for wild mice was 5 s, for domestic mice - 20 s.

In the first generation, there was almost complete dominance of the timidity of wild mice. Among individuals of the second generation, the variability in the degree of fearfulness increased significantly (Fig. 1) compared to F1. Based on his research, Dawson concluded that the difference in fearfulness between wild and domestic mice is determined by two or three genes. Almost all wild mice are homozygous for these dominant genes. In addition to the main genes that determine the degree of fearfulness of the parent generation, several modifiers influence the formation of the studied traits.

This study showed the inheritance of behavioral traits according to Mendelian laws, but at the same time it illustrated that this inheritance is carried out, as in the case of most quantitative differences between traits, with the participation of polymeric genes. The heritability of behavioral characteristics according to the same laws by which morphological characteristics are inherited clearly indicates that the evolution of behavior is carried out as a result of natural (or artificial) selection of hereditary changes. This was pointed out by Charles Darwin in the chapter on instincts in The Origin of Species. At present, significant material has accumulated confirming Darwin's views on this issue.

As an example showing the role of selection in changing the nature of behavior, work on geotaxis in Drosophila melanogaster can be cited. In Fig. Figure 2 shows the results of selection for changes in geotaxis. Selection over 65 generations led to divergence: lines with clearly defined positive and negative geotaxis were created. Reverse selection (carried out between the 52nd and 64th generations) led to a change in the nature of geotaxis. Based on hybridological analysis, the authors come to the conclusion about the polygenic nature of the changes in the behavior of flies, which depend on genes located in the autosomes and the X chromosome.

Along with the hybridological analysis of differences in behavioral characteristics, the phenogenetic method is very important, making it possible to establish the mechanism of hereditary implementation of genotypically determined traits. An example of a simple dependence of the inheritance of various behavioral characteristics on morphological characteristics is the choice of temperature optimum in mice. For example, Herter's work showed that wild mice and albinos choose different temperatures during rest. It turned out that the temperature optimum for wild mice is 37.36°, for white mice - 34.63°. A simple pattern of inheritance of this optimum was discovered. The study showed that the temperature optimum is determined by the thickness of the fur and the thickness of the epidermis on the skin of the mouse's abdomen. White mice have less fur density than wild mice (the number of hairs per unit area is 45:70, and the thickness of the epidermis is greater - the ratio is 23:14). A particularly clear relationship has been established between the temperature optimum and wool density. In hybrids F i ; the temperature optimum is close to the optimum of white mice: it is 34.76±0.12°, the thickness of the coat is 43.71 hairs per unit area.

Rice. 2. Result of selection for positive and negative geotaxis in Drosophila melanogaster (total curves)

The results of reverse selection are shown on a reduced scale (selection of flies with the most negative geotaxis in the positive line and the most positive in the negative line). Bold curves - selection for negative geotaxis; thin - positive. The dots indicate sections of the curve representing generations for which there is no data (according to Erlenmeier-Kimmling et al., 1962).

During backcrossing (F1 - wild mice), splitting into two groups occurred. In one group, the optimum corresponded to that of white mice (+34.56°±0.12) with a fur density of 52.7 hairs; in the other group, the temperature optimum was close to the optimum of wild mice (37°); In this group, the number of hairs per unit area was 70.94. Raising mice at different temperatures, Herter came to the conclusion that, in addition to the hereditarily determined thickness of the epidermis and the thickness of the coat, which determine the temperature optimum, there is also a modified adaptation of each mouse to the temperature in which it is raised. This modification adaptation can change the characteristic optimal choice of a resting place for a given individual. This example clearly showed the dependence of the formation of an adaptive response of behavior on the genotypically determined morphological characteristics of the organism.

An example in which, using the genetic method, it was possible to differentiate the inheritance of a type of behavior from the inheritance of morphological characters was Masing’s work on the study of the photoreaction in Drosophila melanogaster. The study showed that through selection over 26 generations it was not possible to identify a line in which all individuals would or would not react to light. This indicates the incomplete expression of genes that determine the different activity of flies in relation to light. Flies with reduced eyes (Bar, Bar eyeless) react to light, but their reaction is slow. Among eyeless individuals from the eyeless lineage, there are flies that actively respond to light. This showed that the eyes are not the only receptor that perceives light. The sharp weakening of the photoreaction noted in flies with reduced wings gave reason to assume that the photoreceptors are located on the wing. Experiments with wing clipping in flies from a line that actively responds to light led to a significant weakening of positive phototaxis. This confirmed the assumption about the significant role of the wing surface in the photoreaction of flies. However, genetic analysis has shown that this is obviously not the case. The genetic analysis system was carried out in such a way that vestigial flies were crossed with a normal line of flies that actively respond to light. Positive phototropism turned out to be a completely dominant trait. The vestigial flies appearing in F 2 were crossed again with normal flies. After 17 generations of “crossing” of the vestigial gene into the normal line, when the genotypic environment of the vestigial gene was practically replaced by the genotype of normal flies, it turned out that flies with reduced wings began to actively respond to light. This showed that the weak photoreaction of vestigial flies is determined by the unreduced nature of the wings. This study confirmed the view of some entomologists that the perception of light is carried out by the entire surface of the body, and is not associated specifically with the eyes or with the surface of the wing.

An example of the obvious dependence of hereditarily determined behavior on differences in the activity of the gonads is the research of McGill and Blythe, in which it was shown that the onset of sexual activity in males, leading to mating after the previous mating (with ejaculation), is extremely different in different strains of mice. In mice of the C57BL/6 line, this time averaged 96 hours, and in the DBA/2 line – 1 hour. Rapid restoration of sexual activity is dominant. When backcrossing F 1? C57 BL/6 the time for recovery of sexual activity averaged 12 hours; At the same time, a large variation was observed, indicating segregation according to this characteristic.

When studying defensive reactions, it was possible to discover the dependence of the hereditary implementation of behavioral traits on the various functional states of the body. Studies conducted on dogs have shown that the passive defensive reaction (fearfulness, cowardice), which manifests itself in relation to various external factors, is determined by the genotype.

Our work studied defensive behavior in dogs towards humans. In adult dogs, under the same conditions, this property is quite constant. The correlation coefficient between two assessments made 1–2 years apart is +0.87±0.04. Two groups of dogs served as material for the genetic study: the first group (224 individuals) consisted mainly of German shepherds and Airedale terriers, raised in a variety of conditions (kennels and private individuals); the second group included 89 dogs, mostly mongrels. All dogs in this group were raised in the kennel of the Institute of Physiology named after. I. P. Pavlova in Koltushi. The study showed that fear of humans in dogs is a genotypically determined trait that has a dominant or incompletely dominant inheritance pattern. The manifestation and expression of this property of behavior is highly dependent on a number of conditions.

Another defensive reaction, active-defensive (reaction of aggression or malice towards a stranger), was studied by us on 121 offspring obtained from different types of crosses. The criterion for aggressive behavior was the teeth grabbing an object held out to the dog by a stranger. All dogs on this basis are divided into two alternative groups. The correlation coefficient calculated between individual assessments of this trait at intervals of 1–2 years (r=+0.79±0.04) illustrates the rather large constancy of the manifestation of this behavioral trait. The analysis carried out indicates the genetic determination of this behavioral feature, which has a dominant inheritance pattern.

Scott in 1964 published work on the inheritance of the barking response in various breeds of dogs. He established large differences between individual breeds. The greatest differences are found between cocker spaniels, which bark very often, and basenjis (African hunting dogs), which bark almost nothing. The author explains the differences found by the different threshold of dogs’ reaction to external stimuli. In spaniels it is very low, in Basenjis it is high. F 1 hybrids are close to spaniels in their barking reaction. This indicates the dominant nature of inheritance of this property. The nature of the splitting of hybrids showed that the differences found are most easily explained by the presence of one dominant gene, which determines a low threshold for the barking reaction to external stimuli. However, in addition to the inheritance of the main gene, the formation of this behavioral trait is influenced by a large number of modifiers and external conditions.

Passive and active defensive reactions are inherited independently. If they manifest themselves in the same individual, then a kind of maliciously cowardly behavior is formed. When expressed sharply, one of these behavioral components can completely suppress the expression of the other. This was demonstrated by the use of hybridological analysis with the parallel use of pharmacological drugs that change the degree of expression of individual components of the defensive complex of angry-cowardly dogs.

Analysis of the hereditary implementation of defensive reactions of behavior showed that their manifestation and expression are highly dependent on the degree of general excitability of the animal. It turned out that genetically determined behavioral reactions may not appear in the phenotype of an animal if its excitability is low. However, the offspring obtained by crossing such animals with excitable individuals exhibit clearly defined defensive behavior.

Rice. 3. Formation with age of varying degrees of “predominant” behavior of one sex over the other in dogs of different breeds

The x-axis is the age of the dogs; along the y-axis is the percentage of predominant behavior of dogs of one sex over the other, calculated on the basis of the time of acquisition of a bone given to two dogs of different sexes located in the test room for 10 minutes (according to Pavlovsky and Scott, 1956).

Increased excitability is inherited, as has been shown in various animals, as a dominant or incompletely dominant trait. In dogs, increased excitability is inherited as a dominant or incompletely dominant trait. Increased motor activity in rats is a genotypically determined trait and is inherited as an incompletely dominant trait. In Leghorn chickens, according to Golovachev, the threshold of long-term excitability (rheobase) of motor nerve fibers of the sciatic nerve exceeds that in Austrolorp chickens and is a dominant trait, depending on a limited number of genes.

The dependence of the manifestation of cowardly behavior in dogs on different degrees of excitability can be illustrated by the example of crossing German shepherds with Gilyak huskies. Low-excitable, non-cowardly Gilyak Laikas were crossed with excitable, non-cowardly German Shepherds. All descendants of this cross (n = 25) had increased excitability and pronounced cowardice (Fig. 3). In this cross, a genotypically determined passive-defensive reaction was inherited from Gilyak Laikas, in which it did not manifest itself due to the insufficiently high excitability of their nervous system. The presence of a subthreshold passive-defensive reaction in them was proven by artificially increasing the excitability of their nervous system. After the administration of cocaine, Gilyak Laikas showed a passive-defensive reaction. But not only the manifestation, but also the degree of expression of the hereditarily determined reaction of animal behavior depends on the degree of general excitability of their nervous system. By changing the state of excitability of the nervous system, it is possible to change the expression of defensive behavioral reactions. When the degree of excitability increases as a result of the administration of pharmacological or hormonal drugs (thyroid hormone), in parallel with the increase in excitability, an increase in defensive behavior occurs. Conversely, removal of the thyroid gland, which reduces the degree of excitability of the animal, leads to a weakening of defensive reactions.

We studied the dependence of the manifestation and expression of genes that determine these forms of behavior on the genotypically determined activity of the endocrine glands using the example of the inheritance of fearfulness of wild (Norwegian) rats when crossing them with laboratory rats. When using the speed of running a 6-meter corridor as a test while frightening a rat with a sound stimulus, it was found that the fearfulness of wild rats was almost completely dominant in F 1 hybrids. When backcrossing (F 1 - laboratory albinos) a clear split occurred. Wild (Norwegian) rats have a relatively greater weight of adrenal glands compared to laboratory ones due to a more strongly developed cortical layer. In F 1 hybrids, the relative weight of the adrenal glands up to 3 months of age turned out to be intermediate between the size of the adrenal glands of the parents. At older ages, the relative size of the adrenal glands approaches that of laboratory rats. By this age, the increased excitability and fearfulness of F 1 hybrids decreases. Removal of the adrenal glands, as well as the pituitary gland, leading to reduction of the adrenal glands, led to a weakening or even complete elimination of shyness in one and a half month old F 1 hybrids. This weakening of fearfulness occurred against the background of a sharp decrease in general excitability. Thus, in addition to the inheritance of fearfulness genes in wild rats, there appears to be an inheritance of increased functional activity of the adrenal cortex, which causes increased excitability of F 1 hybrids. This example illustrates the presence of some genotypically determined morphophysiological relationships that determine the hereditary implementation of behavioral traits.

Rice. 4. Prolonged motor excitation of a rat after sound exposure (lower picture) and its absence (upper picture)

The lower curve is the mark of the action of stimuli (20 - weak, 130 - strong); the upper curve is a record of the animal’s motor activity (according to Savinov et al., 1964)

A biochemical analysis of the hereditary implementation of defensive behavior and the degree of general activity in mice is carried out by Maas. In this study, two strains of mice were studied: C57 BL/10 and BALB/C. Mice of the first strain are more active, less fearful and have a higher degree of aggressiveness towards individuals of their own species than mice of the second strain. The content of serotonin (5-hydroxytryptamine) and norepinephrine, mediators of nervous system excitation, was studied. The study found that the brainstem (pons, midline, and intermediate) of the C57 BL/10 strain had less serotonin than BALB/C. For the former - 1.07±0.037 mg/g, for the latter - 1.34±0.046 mg/g; the difference is statistically significant: P< 0,01). Достоверных различий в содержании норадреналина не обнаружено. Уровень содержания серотонина в определенных отделах мозга (особенно в гипоталамусе) играет роль в «эмоциональном» поведении животного. Опыты с введением фармакологических препаратов, которые меняют различные звенья обмена серотонина, показали, что найденные генетические различия в содержании серотонина у обеих линий мышей связаны с различными механизмами связывания этого нейрогормона нервной тканью. У мышей линии BALB/C происходит более быстрое освобождение серотонина нервной тканью, чем у мышей линии С57 BL/10. Эти исследования интересны в том отношении, что указывают новые пути возможной биохимической реализации генотипа в формировании особенностей поведения.

The question of the relationship between individually acquired and innate factors is extremely important for the phenogenetics of behavior. Fundamentally, this question does not differ from one of the main problems of phenogenetics: the influence of the genotype and external factors on the formation of morphological characters.

A convenient example for considering the relative role of innate and individually acquired factors in the formation of behavior is the defensive reactions of dogs. The first work carried out by I.P. Pavlov’s employees in Koltushi in 1933 was to study the influence of various conditions of their upbringing on the behavior of dogs. Vyrzhikovsky and Mayorov, dividing two litters of outbred dog puppies into two groups, raised them in different conditions. One group was brought up in isolation, the other in conditions of complete freedom. As a result, the grown dogs of the first group had pronounced cowardice, while the dogs of the second group did not possess it. I. P. Pavlov gave the following explanation for this fact: puppies have a “reflex of natural caution” in relation to all new stimuli; this reflex gradually slows down as one becomes familiar with all the diversity of the external world. If a puppy is not exposed to a sufficient number of diverse stimuli, he remains cowardly (feral) for the rest of his life.

Subsequent studies on the influence of genotype on the manifestation and expression of cowardice depending on the conditions of detention, conducted by us on dogs, showed the interaction of genotypic and external factors in the formation of defensive behavior. The material for this study was German Shepherds and Airedale Terriers (n = 272). Dogs of both breeds were raised in different conditions: one group - with private individuals, where they had the opportunity to come into contact with all the diversity of the outside world, the other - in kennels, where the dogs were in significant isolation from external conditions.

In table 1 shows data on the manifestation and expression of cowardice in these dogs. With isolated upbringing, the percentage of individuals with a passive-defensive reaction increases in both groups. However, among German shepherds, compared to Airedale terriers, the number of cowardly individuals with a sharp expression of this behavioral property increases significantly (this difference is statistically significant).

Table 1. Manifestation and expression of passive defensive reactions in dogs of different breeds raised in different conditions

The data presented indicate that the manifestation and degree of expression of cowardly behavior in dogs raised in isolation depends on the genotype of the animal. Thus, the “wildness” of dogs, which is expressed in the timidity of individuals raised in isolated conditions, is a certain norm of the reaction of the nervous system, determined by the genotype, to the conditions of their upbringing. Despite the fact that the domestication of the dog began no later than 8,000–10,000 years ago (Scott, Fuller, 1965), the modern dog has retained a genotypically determined tendency to become feral, which is easily detected even under slightly isolated rearing conditions.

Dogs taken to areas uninhabited by humans run wild, as happened, for example, in the Galapagos Islands, where they were brought by the Spaniards to destroy goats, which were a source of food for English pirates. This feral dog population exists today. Puppies caught by humans are easily tamed.

The difference in the form of expression of the passive-defensive reaction of free-living populations depending on the different genotype was described by Leopold in 1944. Wild turkeys, domestic and hybrid populations were studied. This population was derived from a cross between wild and domestic turkeys and lived freely in Missouri. Wild turkeys, upon detecting danger at a great distance, immediately fly away. Individuals of the hybrid population, having discovered danger, allow the stranger to come close to them and, having flown away two hundred yards, begin to calmly graze. Wild turkey chicks have a pronounced tendency to hide when an enemy approaches. In the hybrid population, this form of behavior is weakened: the chicks tend to run away or fly away when approached at close range. Studnitz also described differences in the degree of fear of humans in the same bird species living in different geographical locations. The most striking example of this difference in human fear is the blackbird (Turdus viscivorus). In England they are not at all shy, in Northern Europe they are very shy, although they are not persecuted by humans.

The presence in the population of genotypic differences that determine the formation of a passive-defensive behavior reaction is undoubtedly one of the most important factors in the rapid restructuring of defensive behavior when an enemy appears. Such an example was described by F. Nansen. In 1876, when the first ships of the Norwegian fishing fleet penetrated deep into the North, to the shores of Greenland, seals (Cystophora cristata) were so unafraid of people that they were killed with a blow to the head. However, after several years, they became timid: they did not always even allow a rifle shot.

A similar process of increasing fear of humans almost always occurs where a person enters a previously uninhabited territory and begins hunting for animals of the local population. Of course, in addition to the selection of individuals with the most pronounced passive-defensive reaction and individuals who have learned to fear humans more easily than others, tradition can play a large role in the above-mentioned restructuring of defensive behavior in the population. All the various alarm signals, direct imitation of parental behavior can appear, along with selection, by a system of non-hereditary restructuring of population behavior. However, if there are no hereditarily determined prerequisites for the manifestation of a passive defensive reaction, traditional experience alone is apparently unable to determine the fear of an enemy exterminating a given population. Such a case was described by Yu. Huxley using the example of geese of the Falkland Islands. Despite intensive extermination by humans, they showed only slight signs of fear of humans, which did not protect the population from extermination. The presence of genotypic differences in the formation of a passive-defensive reaction is a prerequisite for the restructuring of the defensive behavior of the population. It has been established that the strengthening of the passive-defensive reaction occurs not due to the direct hereditary consolidation of the fear reactions of surviving individuals, but due to the natural selection of the most cowardly individuals or those who had a genotype that contributes to the most rapid formation of fearfulness during their persecution.

Without special genotypic analysis, it is difficult to differentiate hereditary and non-hereditary variability in behavior and traditions from generation to generation. This has long created the conditions for unfounded assumptions of direct inheritance of acquired skills. Even such a strict and objective researcher as I.P. Pavlov, in a very cautious manner, admitted the possibility of inheriting the results of individual experience. In 1913, he wrote: “... it can be accepted that some of the conditioned newly formed reflexes are later transformed by heredity into unconditioned ones” (p. 273). His more definite statement on this issue in his “Lectures on Physiology” dates back to the same period: “Are conditioned reflexes inherited? There is no exact evidence of this; science has not yet reached this point. But one must think that with a long period of development, firmly developed reflexes can become innate” (p. 85). In the early 20s, I.P. Pavlov instructed his employee Studentsov to study the inheritance of conditioned reflexes in mice. These experiments, which did not produce positive results, were often referred to, classifying I.P. Pavlov as a supporter of the inheritance of acquired characteristics. This forced I.P. Pavlov to express his attitude to this issue in a letter to Hutten (Pravda. 1927. May 13). Throughout the rest of his life, I.P. Pavlov stood on a strictly genetic position. He created a laboratory in Koltushi to study the genetics of higher nervous activity, in front of which a monument to Gregor Mendel was erected next to the monument to Descartes and Sechenov. I. P. Pavlov invited the leading geneticist and neurologist S. N. Davidenkov as a permanent consultant in his genetic research; he also consulted with N. K. Koltsov.

Genetic work was carried out through selection in individual families of dogs according to the typological characteristics of their higher nervous activity. The results of these studies, which showed the role of the genotype in the formation of the typological properties of higher nervous activity, were published after Pavlov's death. These studies showed that genotypic factors play a significant role in the formation of typological characteristics of higher nervous activity. In various families of dogs in which selection was made in the direction of the degree of strength (or weakness) of the excitation process, a correlation was observed for these features of nervous activity between brothers and sisters in individual litters of dogs: r = +34 ± 0.1.

The results of crossings between dogs with a strong and weak nervous system, which were started during the life of I.P. Pavlov, are summarized in table. 2.

The degree of nervous system strength is related to gender: males (n = 31) have a stronger nervous system than females (n = 22). The probability of correspondence P(x 2) turned out to be less than 0.05, which can be considered statistically significant. The question of the role of genotypic factors in learning ability has been studied since the well-known works of Yerkes and Bugg. Yerkes studied the learning ability of two strains of rats: one unbred, the other inbred from the Wistar Institute. The results of this work showed that the average learning time of non-inbred lines is slightly less than that of inbred lines (52.25 lessons for the former and 65.00 for the latter). Bugg studied individual and family differences in the way-finding behavior of mice in a fairly simple maze. The line of white mice that Bugg founded in 1913 (line C, now BALB/C) was compared with the line of yellow mice. It turned out that the average learning time for white mice over 15 experiments was 27.5 ± 2.0 s with 9 errors per lesson; the learning time of yellow mice was 83.0 ± 7.0 s with two errors per lesson. There was a similarity in the learning ability of individuals from the same litters.

Table 2. Data on the inheritance of strong and weak types of nervous activity in dogs

A detailed study of the role of genotypic factors in the development of conditioned reflexes was carried out by Vicari. This study examined the learning ability of Japanese dancing mice (Mus Wagneria asiatica) (20 years of inbreeding), three strains of normal mice (Mus musculus), the albino Bugga (14 years of inbreeding), Attenuated Brown (17 years of inbreeding), and abnormal-eyed (abnormal x -ray eyed) (inbreeding 6 years). It turned out that each line of mice has a learning curve characteristic of it. Crosses between individuals of separate lines showed that fast learners dominate over slower learners. The author points out that the nature of the splitting in the second generation suggests that the difference in learning ability between brown and Bugg albinos is caused monofactorially, although the possibility of a more complex pattern of inheritance cannot be denied. Differences in learning ability between the Bugg line and Japanese dancing mice are determined, according to the author, by the presence of several hereditary factors. The study (performed on 900 mice) indicates a large role of genotypic factors in the speed of learning in mice.

However, the differences found in the analysis of such a complex trait as learning speed do not yet prove genotypically determined differences in the intimate mechanisms of the brain associated with the learning process itself. The presence of genotypically determined differences in the unconditioned reflex reactions of the studied lines can largely determine the differences found in learning ability. As a similar example, we can cite the exceptionally thorough work of M. P. Sadovnikova-Koltsova. After studying learning in a maze (Hamptoncourt) in 840 rats, the author, through selection, developed two strains: one that learns quickly, the other that learns slowly. The index of fast-learning rats (logarithm of the time spent on 10 counting experiments) is 1.657±0.025, and that of slow-learning rats is 2.642±0.043. The difference between both indices (D=0.985±0.05) turned out to be 20 times greater than the probable error.

Further analysis showed that the differences found between both strains of rats were not due to differences in their ability to develop conditioned reflexes, but to the greater fearfulness of the second strain of rats (which came largely from wild Norwegian rats). When trained in the Moan apparatus, in which the rat was urged on by slamming doors and therefore could not, due to timidity, hide in the corner of the maze, the training of both lines proceeded in the same way.

Thus, selection did not select genotypes that promote more or less rapid learning, but genotypes that cause varying degrees of timidity, which changed the learning curve. We encounter a similar example of the dependence of the inheritance of the rate of formation of positive conditioned reflexes of chickens and sturgeon on unconditioned reflexes in the work of Ponomarenko, Marshin and Lobashov. The authors explain the inheritance of the characteristics of the excitatory process, which is one of the main parameters in the development of conditioned reflexes, by their correlation with the nature of unconditioned reflexes. In fish, there is a clear dependence of the rate of formation of conditioned reflexes on the level of excitation of the unconditioned food center, which, in turn, depends on the hereditarily determined growth rate. These examples show that when genetically analyzing such a general complex property as learning ability, the most thorough and, if possible, parallel physiological analysis is required.

Geneticists have known for many years that some genes have a pleiotropic effect on morphological and behavioral traits. In 1915, Sturtevant discovered that a recessive gene located at one end of the X chromosome in Drosophila melanogaster, which causes the body to be yellow instead of the normal gray, also reduces the copulatory ability of males.

Further studies showed that the reduced sexual activity of males of this line is associated with a violation of the time and method of “courtship” of females before copulation. Yellow males placed with females begin to court them after an average of 9.6 minutes; normally colored males, after 4.9 minutes. In order for copulation to begin, yellow line males court for an average of 10.5 minutes, normal males - for 6.0 minutes. In addition, in males of the yellow line, one of the main signs of courtship with females is disrupted - the vibration of the wing directed towards the female. This act of behavior by the male is a necessary ritual that the female perceives through her antenna in order to be prepared for copulation. Yellow line males have weaker vibrational beats than normal males and occur at longer intervals.

In lines of yellow flies, females exhibit an increased (statistically significant) readiness for copulation compared to normal females, which is a compensatory adaptation for the possibility of normal mating. This increased willingness to mate in yellow females is not a pleiotropic effect of the yellow gene. It is determined by the selection of other genes that reduce the threshold of copulatory readiness. This example is interesting in that it shows how a single mutation with a pleiotropic effect that changes the behavioral response, and subsequent selection, creates a lineage that, according to the author of this work, Bastok, can lead to the emergence of a physiologically isolated ecotype.

A striking example of the pleiotropic effect of genes on the morphological characteristics and behavioral characteristics of rats is described by Keeler and King. By studying various mutations in coat color that appear in wild (Norwegian) rats kept for many generations in captivity, the authors discovered that the mutant individuals differ from wild ones in their behavior. Mutant individuals with black coat color were especially noticeable in their defensive behavior. Such rats did not bite. The authors believe that their data indicates one of the possible paths along which wild rats were domesticated. They suggest that laboratory albinos arose not as a result of long-term selection of small mutations that changed their “wild” behavior, but as a result of several mutations, some of which had a pleiotropic effect on coat color. A significant role in the domestication of rats was played by the selection of the black coat gene in combination with the piebald gene. In most laboratory albinos, these genes are in the cryptomeric state and are not expressed due to the absence of the main pigmentation factor in albinos.

Studies that have revealed the presence of a broad pleiotropic effect of genes influencing behavior are carried out by Belyaev and Trut on foxes. Studies on silver-black foxes bred in fur farms have shown great heterogeneity of the population in defensive behavioral reactions. Three main types of defensive behavior have been identified: active-defensive (aggressive), passive-defensive (fearful) and calm (absence of both types of defensive behavior). The results of the crosses showed that the largest percentage of foxes with one or another characteristic behavior is observed in the offspring of parents characterized by the same type of behavior: the largest percentage of aggressive foxes is born in the offspring of crossing aggressive individuals; cowardly offspring are found in the greatest percentage when cowardly parents are crossed with each other. Selection for “calm” behavior turned out to be effective. It is important to note that the analysis does not allow us to talk about the influence of one or another type of defensive behavior of the mother on the nature of the behavior of the offspring, which could be formed as a result of imitation. A significant percentage of individuals in fur farms are individuals with cowardly behavior, which is a likely result of isolated rearing (cage housing) of foxes.

A study of the sexual activity of females (time of onset of estrus) and their fertility showed that in calm females, estrus occurred earlier in all age groups than in aggressive individuals. In most groups this difference was statistically significant. A relationship was also found between the nature of defensive behavior and the fertility of females. The highest fertility was found in calm females, the lowest - in angry-cowardly ones. The difference between these groups is statistically significant. Statistically significant differences (in the first year of mating) were also found between the number of offspring of calm females compared to the number of puppies born from angry and cowardly females. An interesting relationship was discovered between behavioral characteristics and coloration. The largest amount of silver (zonally colored) hair is found in foxes with one or another form of defensive behavior. Among the vicious foxes, there was the smallest percentage of individuals with low levels of silver hair. Among foxes selected for a calm form of behavior (such selection turned out to be effective), there were individuals with anomalies in the structure of the fur coat. Since the amount of silver in the fur of foxes increases the value of the skin, it becomes clear why evil and cowardly individuals (less convenient when caring for them) are preserved on farms and why the selection of foxes according to the time of their estrus, which is carried out in fur farming practice, does not give sufficient effect . The research conducted by Belyaev shows the importance of studying the genetics of behavior in selection for economically useful traits in fur farms, opens up new ways of approaching the problem of animal domestication and shows the role of behavior in the formation of morphophysiological characteristics of the population.

The above presented data showing the role of the action of genes on the formation of the behavior of an individual at different levels of its individual development. However, genotypic factors, as has now been discovered, also exert their influence on the behavior of animals through the establishment of various relationships between individuals in individual communities. One of the best-studied ways in which genotype influences group behavior is through the degree of aggression toward conspecifics. In every community of vertebrate animals, as a result of aggressiveness towards individuals of their own species, a behavioral hierarchy is established: some individuals turn out to be “predominant”, others “subordinate”; “subordinate” individuals are afraid of “dominant” ones. The hierarchical system of community behavior depends on many factors. As a rule, young individuals are subordinate to older ones. Outside the breeding season, males are dominant over females. However, during the breeding season, as shown in birds, females begin to dominate over males. Males at the lowest level of the community hierarchy are not selected by female birds for mating. Females who are low in the community hierarchy, if they mate with aggressive, dominant males, themselves begin to occupy a dominant position in the community.

As a number of studies have shown, genotypic factors play a major role in the place that a given individual will occupy in the hierarchy system in the community. This has been clearly shown in mice. Mice of different inbred lines have different degrees of aggressiveness, which determines the hierarchy in the community of these animals. So, for example, of these mouse strains, C57BL/10 (black) mice have the greatest tendency to occupy a dominant position, followed by SZN (zonal gray) mice, and the most subordinate mice are BALB (white) mice.

However, despite the clear role of the genotype in determining the structure of the community in mice, it also became clear that rearing conditions play a large role in the degree of aggressiveness of each mouse. It turned out that mice of easily submissive strains, when raised in isolation, become more aggressive and begin to subdue mice of those strains that were raised in the community. However, if a mouse from a low-aggressive line is raised together with mice from an aggressive line, its aggressiveness increases. Then placed in a community of low-aggressive mice, she will occupy a high place in the hierarchy of subordination.

The genotype plays a major role in the formation of the hierarchical structure of the community in the carnivorous family. Research conducted by Pavlovsky and Scott showed that the degree of dominance in dogs is determined by genotype and varies enormously among different breeds. This difference becomes more pronounced from 11 weeks of age. The clearest predominance (especially of males over females) is found in African hunting dogs (Basenjis) and fox terriers. In beagles and cocker spaniels this predominance is very blurred (Fig. 4). The clearly defined hierarchy of behavior in the dog community makes it extremely difficult for new individuals to join this community. The weakly expressed hierarchy of behavior in beagles and spaniels is, according to the authors, the result of long-term artificial selection, in which the most aggressive individuals were culled, preventing the inclusion of new dogs in the pack. A pronounced hierarchy in the canine community is observed in wild species, such as wolves and the least domesticated breeds of dogs, and is of great biological importance in the struggle for habitat territory.

Thus, several Laika communities are formed in Eskimo villages. Puppies, as a rule, can walk around the entire village with impunity. However, after the onset of puberty, when they begin to mate, each dog joins a community and then bites into pieces if it enters the territory occupied by another community (Tinbergen).

Wild animals usually form a community consisting of a varying number of members. This may be a family or a herd that is not directly related. One of the main reasons determining the formation of such communities is the protection of the occupied territory from the penetration of members of other communities into it. The number of individuals included in a community is largely determined by genotype, as was shown in Leopold's work on turkeys. It turned out that wild turkeys form smaller flocks than individuals of the hybrid population.

Thus, genotypically determined aggressiveness towards individuals of its own species has biological significance. Firstly, it promotes the formation of physiologically isolated groups of biotypes, which is the most important condition for speciation. Secondly, by creating a hierarchical system of behavior, aggressiveness places the weakest individuals in the least favorable conditions for reproduction, which favors the negative selection of the least adapted individuals. And finally, thirdly, aggressiveness towards individuals of one’s own species leads, as was vividly shown by K. Lorenz using the example of the struggle for existence carried out among coral reef fish, to a uniform distribution of individuals of the same species throughout the territory habitat, which determines its most rational use.

Thus, the specificity of the action of genes comes down to the fact that they not only play a crucial role in shaping the behavior of an individual, but also largely determine the relationships of animals within individual communities, thereby influencing the formation of the population structure and the course of the evolutionary process.

The use of genetic methods to study the physiological mechanisms underlying pathological disorders of higher nervous activity is clearly evident from the intensive study in many countries of the world of hereditary diseases of the nervous system in animals.

The most widely studied genetic model of nervous system disease is experimental rodent epilepsy. In 1907, a mutation was discovered in Vienna White rabbits, in which epileptic seizures developed under the influence of various nonspecific external stimuli. Nachtsheim, through inbreeding, achieved seizures in 75% of the rabbits of his line. He concluded that the predisposition to seizures is determined by a single recessive gene. However, several modifiers have an inhibitory effect on the hereditary implementation of this behavioral feature. The Nachtsheim line of rabbits died during the Second World War.

Currently, a line has been bred in which almost 100% of individuals respond with convulsive seizures in response to strong sound stimuli.

Convulsive seizures in mice and rats have become widespread as an experimental model of epilepsy. Wieth and Hall studied the genetics of seizures (called audiogenic or reflex epilepsy) in mice produced by an auditory stimulus (usually an electric bell at 100–120 dB). The authors crossed two inbred lines: C57 BL, in which convulsive seizures develop in response to sound stimulation in 5% of cases, with the DBA line, in which seizures develop in 95% of individuals. They concluded that an increased susceptibility to seizures is determined by a single dominant gene. However, subsequent studies conducted on the same mouse strains did not confirm the monofactorial picture of the study. Ginsburg and Starbook-Miller, as a result of their long-term inheritance, come to the conclusion that the similar phenotypic expression of seizures observed in different substrains of mice (C57 BL/6 and C57 BL/10, DBA/1 and DBA/2) has a different genetic basis . It is most likely that the seizure-sensitive DBA sublines have the genetic formula AABB, and the insensitive C57 BL sublines have two recessive alleles aABB. Each of these genes is located on a different autosome. The most likely difference in the degree of dominance and the ratio of sensitive and insensitive individuals in F 2 and backcrosses is explained by the difference in each of the lines used in a number of modifier genes.

Physiological studies carried out in parallel with genetic analysis showed that the susceptibility to epileptic seizures in mice is associated with their general susceptibility to stress factors. In this case, oxidative-phosphorylation mechanisms, which are different in the studied strains of mice, seem to be especially important.

The phenotypic appearance and expression of convulsive readiness in mice is greatly influenced by various external factors. A striking example of such an effect is the increase in convulsive readiness of DBA/1 mice and their hybrids obtained from crossing with C57 BL mice under the influence of very small doses of radium. Mice that were chronically exposed to gamma rays for a month from birth (total dose 0.14 rad) were found to be hypersensitive to the sound stimulus.

A change in the general background radiation also affects the sensitivity of mice to the action of a sound stimulus. From May to October 1957, Starbook-Miller found a significant increase in the number of convulsive seizures during sound exposure in mice of the DBA/1 line in Fi, obtained from crossing with C57 BL. According to the Atomic Energy Commission, this period coincided with an increase in overall radiation levels in America.

The development of convulsive seizures in rats under the influence of a sound stimulus is also determined genotypically. In the population of laboratory rats and the Wistar rat line, about 10–15% of individuals develop convulsive seizures in response to a sound stimulus (100–120 dB bell).

As a result of selection, we were able to obtain a line of rats that produce convulsive seizures when exposed to sound in 98–99% of individuals. Despite the clear genotypic determination of this pathological reaction in rats, the exact pattern of its inheritance is unclear. Data published by various authors are contradictory. The data obtained by L.N. Molodkina and me only indicate the obvious incomplete dominance of the increased sensitivity of rats to the action of sound stimuli. When crossing rats of our line with insensitive unselected rats and rats of the Wistar line in the first generation, 93 (69.9%) were sensitive individuals, 40 (30.1%) were insensitive.

Based on the nature of splitting in subsequent generations, it is still difficult to draw a conclusion about the number of hereditary factors that control the development of this pathology. However, in the complex complex of reactions of rats to a sound stimulus, it was possible to identify more simply inherited features of nervous activity. Prolonged excitement turned out to be such a property. It is expressed in the fact that after several minutes (according to our standard 8) of sound exposure, the rat, despite turning off the stimulus, continues to be in a state of strong motor excitement, sometimes lasting tens of minutes (Fig. 4). This property was discovered in a striking form in one male of our sensitive line. As a result of selection and inbreeding, this feature of nervous activity was fixed. Prolonged excitation turned out to be a recessive trait in relation to the absence of this functional property of nervous activity: all 68 F i hybrids sensitive to sound stimuli, obtained from crossing rats of our line with unselected rats and rats of the Wistar line, in which this property is absent, turned out to be without protracted excitation. When F 1 was backcrossed with linear rats with prolonged excitation, out of 93 individuals sensitive to the sound stimulus, 70 were without prolonged excitation and 23 with prolonged excitation. This split is consistent with the hypothesis that prolonged excitation is caused by two recessive genes. In this case, the expected split should be 69.75:23.25. However, when rats with prolonged arousal are crossed with each other, those obtained from this crossing, along with rats with prolonged arousal, are also born individuals without it. This indicates that the analyzed trait is controlled more complexly than by two recessive genes, which appear in 100% of cases. Breeding a line of rats highly sensitive to sound stimulation and possessing prolonged arousal was a crucial step for the possibility of conducting pathophysiological studies. In addition to epileptic seizures, rats of our line develop a number of pathologies: the most important of them relate to the cardiovascular system - death from cerebral hemorrhages, changes in blood pressure, functional disorders (arrhythmias) of cardiac activity, etc. The main reason for the development of all these pathology is the excitation of the brain under the influence of a sound stimulus. The genotypic determination of the excitation threshold and the strength of protective-inhibitory processes, on the one hand, and the functional state of the nerve centers, depending on a number of external factors, on the other, determine the picture of developing excitation. However, despite the multiplicity of factors involved in the development of this pathology, relatively simple relationships between the process of excitation and inhibition determine the variety of observed stages of this process. These relationships, as shown by Savinov, Krushinsky, Fless and Wallerstein, obviously boil down to the fact that excitation during the time of action of the sound stimulus grows, approaching a curve that has a linear character, and the inhibitory process limiting this excitation grows exponentially.

Research conducted on the genetics of behavior has established a number of facts.

Firstly, it has been shown that many behavioral acts are controlled by a small number of genes, inherited according to Mendelian laws. As a result of a combination of independently inherited acts of behavior, forms of behavior that are more complex, holistic in their manifestation and expression are formed, which can be dissected by both genetic and physiological methods. At the same time, a complex morphophysiological complex, such as domestication, can be determined by the selection of a small (even one) number of genes that have a pleiotropic effect on behavior and morphological characters.

Secondly, genetic control of behavior occurs at various levels of organization. Differences in behavior have been found that are controlled by genes that act at the cellular level, by genes that control the biochemical and physiological processes underlying different types of behavior, and, finally, by genes that act at the behavioral level, thereby determining different population structures. With the clarification of the role played by genotypic factors that control behavior in the formation of individual isolated microbiotypes in a population, and the establishment of the role of genotypic factors in different types of activity, a new direction is opening in the study of the role of genetics in evolution and biogeocenology.

Thirdly, the hereditary implementation of behavioral reactions is extremely dependent on individual experience. Acts of behavior that are similar in their external manifestation may be due to various reasons. In some cases, they are formed under the leading influence of innate factors, in others - under the leading influence of individual experience. The difficulty in distinguishing between hereditary and non-hereditary variability of behavior without special genotypic analysis and the possibility of transmission through imitation of certain traditions from generation to generation have long created the conditions for unfounded assumptions of direct inheritance of individually acquired skills.

Fourthly, the genotypic conditionality of pathological reactions of nervous activity, similar to human diseases, has been established. Certain genotypically determined shifts are detected in general biochemical and physiological systems, which may underlie a wide range of pathological reactions of the body. This opens up the possibility of studying in model experiments on animals with a certain genotype the biochemical and physiological mechanisms that underlie the development of a number of pathologies encountered in the clinic.

There is no doubt that the convergence of genetics and physiology of higher nervous activity will not only enrich both of these sciences, but will also have a great influence on a number of other branches of biology.

Notes:

Experienced pedometer readings obtained after injection; Pedometer benchmarks obtained before injection.

Journal total biology. 1944. T. 5, No. 5. pp. 261–283.

Current issues of modern genetics. M.: Moscow State University Publishing House, 1966. pp. 281–301.

Pavlov I.P. Lectures on physiology. L., 1952.

Despite the fact that there is continuous variability in the degree of strength between the individuals studied, in the table below all dogs are divided into two alternative groups: weak and strong.

Stress factors are understood as various nonspecific irritants that lead to profound disruptions in the body’s regulatory mechanisms.

23072 04.06.2005

A study conducted in New Zealand is worthy of mention. This study made scientists think about whether it is even legitimate to talk about a hereditary predisposition (tendency) to antisocial behavior. Perhaps a more accurate concept would be the genetically determined vulnerability (insecurity) of some children in relation to adverse, traumatic events

There have been publications about adoption on our website more than once. Potential adoptive parents have many questions about the heredity of children from disadvantaged families. We publish an article by M.V. ALFIMIVA, candidate of psychological sciences, leading researcher at the laboratory of clinical genetics of the Scientific Center for Mental Health of the Russian Academy of Medical Sciences, on whether behavior is inherited.

What is the heritability of a psychological trait?
People differ from each other in a number of psychological characteristics. These differences are caused by both different living conditions and dissimilar genotypes, since people's genotypes contain different forms of genes. Psychogenetics studies the relative contribution of heredity and environment to the diversity of people in terms of psychological properties and behavior. To assess the influence of heredity and environment on human behavior, scientists compare people with different degrees of genetic commonality (identical and fraternal twins, siblings and half-siblings, children and their biological and adoptive parents).
Many genes exist in multiple forms, just as there are different forms of the gene that determines eye color. Some genes have dozens of forms. The genotype of a particular person contains two copies of each gene, the forms of which may be different or may be the same. One is inherited from the father, the other from the mother. The combination of forms of all genes is unique for each human body. This uniqueness underlies genetically determined differences between people.
The contribution of genetic differences to the diversity of people in psychological properties is reflected in an indicator called the “heritability coefficient”. For example, for intelligence the heritability rate is at least 50%. This does not mean that 50% of intelligence is given to a person by nature, and the remaining 50% must be added through training, then intelligence will be 100 points. The heritability coefficient is not related to a specific person. It is calculated to understand why people differ from each other: whether the differences arise because people have different genotypes, or because they were taught differently. If the heritability coefficient of intelligence turned out to be close to 0%, then we could conclude that only learning creates differences between people and the application of the same educational techniques to different children will always lead to the same results. High values ​​of the heritability coefficient mean that even with the same upbringing, children will differ from each other due to their hereditary characteristics. The end result, however, is not determined by genes. It is known that children adopted into prosperous families are close to their adoptive parents in terms of intellectual development and can significantly exceed their biological ones. What then is the influence of genes? Let us illustrate this with the example of a specific study.
Scientists examined two groups of adopted children. Conditions in the adoptive families were equally good for all, and the children's biological mothers differed in their level of intelligence. The biological mothers of children from the first group had above average intelligence. Approximately half of the children from this group demonstrated above average intellectual abilities, the other half - average. The biological mothers of the children in the second group had slightly reduced (but within normal limits) intelligence. Of this group, 15% of children had the same low intelligence scores; the remaining children had an average level of intellectual development. Thus, under the same conditions of upbringing in foster families, the intelligence of children, to a certain extent, depended on the intelligence of their blood mothers.
The above example can serve as an illustration of the significant differences between the concept of heritability of psychological qualities and the heritability of certain physical characteristics of a person, such as eye color, skin color, etc. Even with a high level of heritability of a psychological trait, the genotype does not predetermine its final value. How a child will develop under certain environmental conditions depends on the genotype. In some cases, the genotype sets the “limits” for the expression of a trait.

The influence of heredity on intelligence and character at different ages
Research shows that genes are responsible for 50-70% of the diversity of people in terms of intelligence and for 28-49% of the differences in the severity of the five “universal” most important personality traits:
- self-confidence,
- anxiety,
- friendliness,
- consciousness,
- and intellectual flexibility.
This information is for adults. However, the degree of influence of heredity depends on age. The results of psychogenetic studies do not support the widespread belief that with age, genes influence human behavior less and less. Genetic differences tend to become more pronounced in adulthood, when character has already been formed. The values ​​of the heritability coefficient for most of the studied psychological properties are higher for adults than for children. The most accurate data have been obtained on the hereditary conditioning of intelligence. In infancy, the intrapair similarity of fraternal twins is as high as for identical twins, but after three years it begins to decline, which can be explained by the greater influence of genetic differences. At the same time, the increase in differences does not occur linearly. There are stages in the development of a child in which differences between children are caused primarily by environmental influences. For intelligence this is the age of 3-4 years, and for the formation of personality - pre-teen age 8-11 years.
In addition, different genetic factors operate at different ages. Thus, among the hereditary factors that cause differences in intelligence, there are both stable, i.e., acting at all ages (these are possibly genes associated with the so-called “general intelligence”), and specific for each period of development (probably some genes that determine the development of private abilities).

The influence of heredity on antisocial behavior
Since in all developed countries, crime and alcoholism of biological parents are common reasons for a child losing his birth family and being placed in foster care, we will take a closer look at psychogenetics data on the influence of heritability on these forms of behavior. Family and twin studies of criminal behavior have been conducted for more than 70 years. They give very different heritability estimates, most often falling in the 30-50% range. “Upper” heritability values ​​are obtained by studying twins. Some researchers believe that the twin method may overestimate heritability because it does not always separate genetic influences from the special environmental conditions in which identical twins grow up. By studying adopted children, heritability coefficient values ​​are approximately 2 times lower than when studying twins.

Danish Study of Adopted Children
(cm. )

The most systematic studies of the heritability of criminal behavior by studying adopted children were carried out in the Scandinavian countries - Denmark and Sweden. Thanks to the cooperation of adoptive parents and a number of government agencies, Danish scientists were able to trace the fate of more than 14,000 people adopted between 1924 and 1947. Figures 1 and 2 show the results of a study of criminal records among men raised in foster care. They refer only to property crimes because the number of violent crimes was small.

Picture 1 . Number of families analyzed, differing in the criminal record of the biological father and the adoptive father (Danish study).

Figure 2. Proportion of sons with a criminal record in families that differ in the criminal record of the biological father and the adoptive father (Danish study).

From Figure 2 it can be seen that the proportion of convicts among children whose biological fathers were criminals is slightly increased compared to those children whose biological parents did not break the law. In addition, it turned out that the more criminal records a biological father has, the higher the risk for the offspring of becoming a criminal. It has also been shown that brothers adopted from different families tended to be concordant in criminal behavior, especially when their biological father was a criminal. These data indicate a certain role of heredity in increasing the risk of criminal behavior. However, as from the above example with intelligence, from the data in Figure 2 it follows that unfavorable heredity does not predetermine the future of the child - of the boys whose biological fathers were criminals, 14% subsequently violated the law, the remaining 86% did not commit illegal actions.
In addition, it turned out that the adoptive family has a particularly strong influence on children with unfavorable heredity, which can be both positive and negative. Of the boys who grew up in foster care, 16% subsequently committed crimes (versus 9% in the control group). Among the biological fathers of these children, 31% had problems with the law (versus 11% in the control group). That is, although the crime rate among adopted children was higher than the average in society, it was almost two times lower than among their biological fathers. According to a number of scientists, this indicates that a favorable environment in a foster family reduces the risk of criminal behavior in children with a family history.
But in some cases, the family environment can increase the risk of criminal behavior. As can be seen from Figure 2, children whose biological and adoptive fathers had criminal records committed crimes more often than others. (Fortunately, there were very few such families (Fig. 1)). This means that there are genotypes that have increased vulnerability to unfavorable aspects of the family environment (such phenomena in psychogenetics are called genotype-environment interaction).

Swedish study
In a study of adopted children in Sweden, scientists initially did not find even a weak connection between the criminal records of children raised by adoptive parents and the behavior of their biological fathers.
Among Swedes, crime was mainly a consequence of alcohol abuse. When the scientists excluded this type of crime from the analysis, they found a weak positive relationship between the criminal records of offspring and their blood fathers (Figure 3). At the same time, the crimes in both generations turned out to be not serious. These were mainly thefts and fraud.
The sensitivity of children with hereditary burdens to the characteristics of the adoptive family was also confirmed. There was no increase in crime rates among adopted Swedes compared to the national average, despite the fact that the conviction rate was increased among their biological parents. Among the Swedish adoptive parents there were no persons with a criminal record. Those. the most favorable family environment “neutralized” the effect of the genetic load.
On the other hand, the highest risk of breaking the law was observed in those children with unfavorable heredity whose adoptive family had a low socio-economic status (Fig. 3).

Figure 3 . Percentage of criminal convictions among adopted persons by family type (Swedish study).

American study
Scandinavian studies included analyzes of the behavior of adopted children born in the first half of the 20th century. Similar results were obtained in modern work by American scientists from Iowa. True, it was not a criminal record that was analyzed, but the presence in adopted children of a tendency towards antisocial behavior of a wider spectrum. Behaviors that would lead to a diagnosis of antisocial personality disorder were assessed and included frequently engaging in arrestable behavior, as well as traits such as deceit, impulsiveness, irritability, disregard for safety, irresponsibility, and lack of conscience. We also took into account a number of characteristics of the adoptive family that could influence the formation of such inclinations. Figure 4 lists these characteristics and shows the main findings of the study when adoptees reached adulthood (ages 18 to 40). Only data on men were analyzed because the number of women with “antisocial behavior” was too small. Of the 286 men studied, forty-four were diagnosed with antisocial personality disorder. The results indicated that three factors make an independent contribution to the development of this disorder: 1) the criminal record of the biological parent (genetic), 2) drunkenness or antisocial behavior of one of the members of the adoptive family (environmental), 3) the placement of a child with unfavorable heredity in a family with a low social -economic status (genotype-environmental interaction).

Figure 4. The results of a study of the reasons leading to the formation of an antisocial personality in an American study of adopted children (arrows indicate a statistically significant relationship between the characteristics of parents and the formation of antisocial tendencies in children).

What is a hereditary predisposition to antisocial behavior?
Obviously, in humans, genes do not trigger specific behavior in the same way as they do with some instinctive actions of animals. The relationship between the risk of criminal behavior and genes is mediated by psychological characteristics. Moreover, it is known that the risk of criminal behavior can be influenced by various unfavorable combinations of psychological properties, and each of these properties is under the control of several or a large number of genes and various environmental factors.

The first candidate for the role of a biological “substrate” of antisocial tendencies was the Y chromosome (a chromosome that is found only in the genotype of men and determines male sex). About one in 1,100 men, as a result of biological errors in the complex process of creating a germ cell, ends up with two or more Y chromosomes instead of one. These men are distinguished by low intelligence (at the lower limit of the norm) and tall stature. In the 60s of the 20th century, it was first shown that among criminals serving sentences with reduced intelligence, a disproportionate number (4%) of men with an extra Y chromosome. At first, the connection between this genetic defect and criminal tendencies seemed obvious: since men are more aggressive than women, commit crimes more often, and, unlike women, have a Y chromosome, the presence of two or more Y chromosomes should lead to the formation of an aggressive “super man.” But later it turned out that criminals with an extra Y chromosome are no more aggressive than other prisoners, and they end up in prison mainly for committing thefts. At the same time, in men with this genetic pathology, a connection was found between a decrease in intelligence and the likelihood of being convicted. It is possible, however, that reduced intelligence did not affect the risk of committing a crime, but the risk of being caught and imprisoned. For example, one of the men with an extra Y chromosome broke into houses several times while the owners were in the room.

Studies of men with an extra Y chromosome lead to at least two important conclusions. First, the relationship between genes and crime cannot be explained by a genetically determined increase in aggressiveness or cruelty, as “common sense” might suggest. This conclusion is consistent with data from studies of adopted children, in which the influence of heredity was found only for crimes against property. Secondly, even among men with such an obvious hereditary anomaly as an extra Y chromosome, the majority do not become criminals; we are only talking about a slight increase in the risk of such behavior among them.

Since the mid-90s, scientists have been searching for specific genes that could influence the risk of criminal behavior. All data obtained to date still needs confirmation and clarification. However, a study conducted in New Zealand deserves mention. It showed that among boys who had been abused in their families, carriers of a form of the gene that provides higher activity of the MAOA enzyme in the body were less likely to engage in antisocial behavior than carriers of another form of the gene - a low-activity one. Among children who grew up in prosperous families, there was no connection between antisocial tendencies and the MAOA gene. That is, individuals with certain genetic characteristics turned out to be less vulnerable to parental abuse. This study made scientists think about whether it is even legitimate to talk about a hereditary predisposition (tendency) to antisocial behavior. Perhaps a more accurate concept would be the genetically determined vulnerability (insecurity) of some children in relation to adverse, traumatic events.

The influence of heredity on alcohol abuse
It has long been noted that crime and alcohol abuse are closely related. Moreover, psychogenetic studies have suggested that there are “predisposition genes” common to these forms of behavior. Some similar patterns have also been identified in the influence of heredity and environment on crime and alcohol abuse. For example, for both forms of behavior, a significant influence of the general environment is found in adolescence. The influence of the common environment is manifested, in particular, in the fact that brothers and sisters growing up in the same family (even if they are not related) are more similar to each other in antisocial manifestations and habits associated with drinking alcohol than to their parents. However, alcohol abuse is a rather complex phenomenon from a behavioral and genetic point of view, since it includes everyday drunkenness and alcoholism as a gradually developing mental illness (the main diagnostic sign of which is an irresistible psychological attraction to alcohol). Obviously, the role of genes in these two cases is different, but it can be quite difficult to separate these two forms of alcohol abuse in a psychogenetic study. This may be why estimates of the heritability of alcoholism vary widely. The most likely range seems to be 20-60%. Among the sons of patients with alcoholism, according to various sources, on average 20-40%, and among daughters - from 2% to 25% (on average about 5%). At the same time, it can be considered established that the age at which they began to drink alcohol and the intensity of its consumption in the first stages is completely determined by the influence of the environment. Note that drinking alcohol at an early age (usually before 15 years of age) is a risk factor for the development of alcoholism. The absence of genetic influences on this trait indicates the important role of parental behavior that inhibits adolescent alcohol use in preventing the development of alcohol dependence. At the same time, genetic effects and genotype-environmental interactions are clearly detected in the further escalation of alcohol consumption and the development of alcoholism.
Let us emphasize, however, once again that a person is not born an alcoholic and there is no one “alcoholism gene,” just as there is no “crime gene.” Alcoholism is the result of a long chain of events that accompany regular drinking. A large number of genes influence these events to some extent. So, it depends on the character of a young man how often he will drink and whether he will know when to stop, and character, as already mentioned, depends on both upbringing and genotype. In addition, due to their genetic characteristics, people are sensitive to the toxic effects of alcohol to varying degrees. For example, some Japanese, Koreans and Chinese have found this form of a gene that affects the processing of alcohol in the liver, the possession of which leads to very severe alcohol poisoning. A person with this form of the gene, after drinking alcohol, feels nausea, flushing, dizziness and irritation. These unpleasant sensations keep a person from further drinking alcohol, so among carriers of this form of the gene there are almost no alcoholics. Finally, not all people who regularly drink alcohol develop an irresistible craving for it. There are genes (they are now being intensively searched) that determine whether the long-term effect of alcohol on the brain will lead to alcohol dependence. At the same time, genes do not trigger specific forms of behavior, they do not “force” a person to go and drink. If a person knows they are susceptible to alcoholism, they can avoid situations that encourage drinking and remain healthy.
Children of alcoholics are often called a multiple-risk group. About 1/5 of them have various problems that require special attention from parents, teachers, and sometimes doctors. Mostly these are restlessness and neurotic disorders (tics, fear of the dark, etc.). Difficulties in mastering the school curriculum are observed less frequently, and other more serious disorders, for example, convulsive conditions, are even less common. These disorders are not manifestations of any defects in the genetic apparatus and are caused by unfavorable conditions in which mothers carry their pregnancies and raise their babies. Studies of adopted children have shown that alcoholism of birth parents does not increase the likelihood that the child will develop any serious mental disorder in the future.
Summarizing the existing data on the influence of heritability on antisocial behavior and alcoholism, the following conclusions can be drawn.
- There is a positive, although very weak, connection between the criminality of blood fathers and their sons who grew up in foster families.
- This pattern is found only for minor crimes, so there is no reason to believe that the risk of becoming a criminal in adopted children is explained by a genetically determined increase in aggressiveness or cruelty.
- Data indicate that a favorable family environment can neutralize innate characteristics associated with an increased risk of criminal behavior, while an unfavorable family environment can enhance them.
- The development of antisocial tendencies is not inevitable even among carriers of serious genetic abnormalities.
- The age at which they started drinking alcohol and the intensity of its consumption in the first stages is completely determined by the action of various environmental factors. Genetic effects and genotype-environment interactions are detected only for the subsequent escalation of alcohol consumption and the development of alcoholism.

Willerman L. Effects of families on intellectual development. Quote according to “Psychogenetics” by I. V. Ravich-Shcherbo et al.
Environmental influences in psychogenetics are divided into general and individual environments. The common environment refers to all non-hereditary factors that make compared relatives from the same family similar to each other and not similar to members of other families (we can assume that for psychological properties these are parenting styles, the socio-economic status of the family, its income, etc.). The individual environment includes all non-hereditary factors that form differences between family members (for example, a unique circle of friends, classmates or teachers for each child, memorable gifts or actions of adults, forced isolation from peers as a result of some kind of trauma or other individual events).

Behavioral genetics

(behavioral genetics) - a field of knowledge that studies genetic and trace determinants in variability animal behavior and psychological characteristics of a person (in the latter case the term human behavioral genetics is sometimes used). In Russian, in relation to the study of a person, it is more appropriate to use the term, since it is understood as a set of external actions and actions of a person, and the scope of this concept does not include, for example, sensory thresholds, psychophysiological features (see), formal characteristics of cognitive processes, etc.

Brief psychological dictionary. - Rostov-on-Don: “PHOENIX”. L.A. Karpenko, A.V. Petrovsky, M. G. Yaroshevsky. 1998 .

Behavioral genetics

A branch of genetics devoted to the study of patterns of hereditary conditioning of functional manifestations of the activity of the nervous system. The main task is to describe the mechanisms of implementation of genes in behavioral traits and highlight the influence of the environment on this process. Along with other research methods, the genetic selection method is used here, thanks to which the properties of the nervous system and behavioral characteristics can be purposefully changed. Each heritable behavioral trait usually has a complex polygenic character. Animals from lower levels of the evolutionary ladder (insects, fish, birds) are characterized by low variability in innate, instinctive actions determined by genotype. With evolutionary development, the process of formation of conditioned reflexes becomes increasingly important, and the genotype determines phenotypic variability less and less. Information important for adaptation is not only acquired in one’s own experience, but can be transmitted from parents to offspring through direct contacts, due to imitative conditioned reflexes. Data obtained in the genetics of behavior are of particular importance for the study of human nervous activity in pathologies: often mental retardation and mental illnesses are hereditary and associated with genetic disorders.

Dictionary of a practical psychologist. - M.: AST, Harvest. S. Yu. Golovin. 1998.

Behavioral genetics Etymology.

Comes from the Greek. genоs - origin.

Category.

Genetics section.

Specificity.

Dedicated to the study of patterns of hereditary conditioning of functional manifestations of the activity of the nervous system. Its main task is to describe the mechanisms for the implementation of genes in behavioral traits and to highlight the influence of the environment on this process. Each inherited behavioral trait, as a rule, has a complex polygenic character. Animals at lower levels of the evolutionary ladder (insects, fish, birds) are characterized by low variability in innate, instinctive acts determined by genotype. As the process of formation of conditioned reflexes acquires increasing importance in evolutionary development, the genotype determines phenotypic variability less and less. Information important for adaptation can not only be acquired through personal experience, but also transmitted from parents to offspring on the basis of direct contacts, through imitative conditioned reflexes. Data obtained in behavioral genetics are of particular importance for the study of human nervous activity in pathology: often mental retardation and mental illnesses are hereditary and associated with genetic metabolic disorders, changes in the number and structure of chromosomes.

Methods.

Psychological Dictionary. THEM. Kondakov. 2000.

BEHAVIOR GENETICS

(English) behavioral genetics) - a branch of genetics that studies the patterns of hereditary determination of the structural and functional characteristics of n. With. G. p. allows us to understand the nature of the hereditary transmission of behavioral characteristics; reveal unfolding in ontogenesis chain of processes leading from genes to traits; isolate the influence of the environment on the formation behavior within the limits of potential given genotype.

Using genetic selection method properties n.With. and behavioral characteristics m.b. directionally changed. The inheritance of differences in behavioral traits is, as a rule, complex polygenic in nature.

It has been experimentally shown that the species stereotype of animal behavior has a very strict hereditary conditionality. Low variability of innate, instinctive acts is especially characteristic of animals standing at lower levels of the evolutionary ladder - insects, fish, birds, however, even in insects the behavior can be modified by production temporary connections. Moreover, behavior is not a simple result of evolutionary changes; it plays an active role in evolution, since through behavioral adaptations the effect of selection is manifested in the animal population and the regulation of its structure and numbers is ensured. Hereditary information from parents to descendants can be transmitted on the basis of direct contacts, due to the development of imitative conditioned reflexes and other ways of perceiving and transforming information (the so-called signal heredity).

Of particular importance for genetic research is the study of human nervous activity—in normal and pathological conditions. Often and mental illnesses have a hereditary etiology associated with genetic metabolic disorders, changes in the number and structure of chromosomes, etc. disorders of the genetic apparatus. Cm. . (I.V. Ravich-Scherbo.)

Large psychological dictionary. - M.: Prime-EVROZNAK. Ed. B.G. Meshcheryakova, acad. V.P. Zinchenko. 2003 .

Behavioral genetics

Field of study concerned with the genetic basis of behavior. The main thesis of this approach is that genetic differences largely explain the differences between people and their responses to the environment.

Psychology. AND I. Dictionary reference / Transl. from English K. S. Tkachenko. - M.: FAIR PRESS. Mike Cordwell. 2000.

See what “behavior genetics” is in other dictionaries:

Genetics of Behavior- a doctrine developed by J. Piaget, at the center of which is the study of psychological mechanisms that determine the structure and development of knowledge. It makes an attempt to combine the data obtained in the experiment... Psychological Dictionary

Behavioral genetics- a field of behavioral science based on the laws of genetics (See Genetics) and studying to what extent and in what way differences in behavior are determined by hereditary factors. Basic methods of studying G. p. on experimental ...

Behavioral genetics- a science that studies the role of hereditary factors in the formation of animal behavior. It is believed that most behavioral traits are controlled by many genes (polygenic inheritance) and environmental factors. Probably the more difficult... ... Trainer's Dictionary

Behavioral genetics- (behaviour genetics), the science of the genetic basis of behavior and psychologist, the savior of man. Arguments in favor of the determination of behavior by hereditary factors center around the dilemma: nature or nurture, i.e. Does it… … Peoples and cultures

Behavioral genetics- [Greek gengtikos related to birth, origin] a field of knowledge that studies genetic and environmental determinants in the variability of animal behavior and human psychological characteristics (in the latter case the term is sometimes used ... ... Encyclopedic Dictionary of Psychology and Pedagogy

Behavioral genetics- a branch of genetics that studies the connection and dependence of the hereditary gene program of a person (and in general of any living organism) and its behavior. Here the patterns of hereditary transmission of the properties of genes to the qualities and properties of human are revealed... ... Fundamentals of spiritual culture (teacher's encyclopedic dictionary)

- (behavior genetics). Study of the relationship between behavior and the genetic structure of an individual... Developmental psychology. Dictionary by book

Behavioral genetics- G.P. is nothing more than the application of genetic principles and laws to the study of behavioral variables. Intelligence, personality and psychology. anomalies are made up of three main factors. research areas in psychology, where G. p. Po’s methods are widely used... ... Psychological Encyclopedia

Genetics Great Soviet Encyclopedia

Genetics- I Genetics (from the Greek génesis origin) the science of the laws of heredity and variability of organisms. The most important task of G. is the development of methods for managing Heredity and hereditary Variability in order to obtain the forms that a person needs... ... Great Soviet Encyclopedia

Behavioral genetics (eng. behavioral genetics)- a branch of genetics that studies the patterns of hereditary determination of structural and functional characteristics of n. With.

behavioral genetics allows us to understand the nature of the hereditary transmission of behavioral characteristics; reveal the chain of processes unfolding in ontogenesis leading from genes to traits; isolate the influence of the environment on the formation of behavior within the potential capabilities specified by the genotype. Using the genetic selection method, the properties of n. With. and behavioral characteristics m.b. directionally changed. The inheritance of differences in behavioral traits is, as a rule, complex polygenic in nature.

It has been experimentally shown that the species stereotype of animal behavior has a very strict hereditary conditionality. Low variability of innate, instinctive acts is especially characteristic of animals standing at lower levels of the evolutionary ladder - insects, fish, birds, however, even in insects the behavior can be modified due to the development of temporary connections. Moreover, behavior is not a simple result of evolutionary changes; it plays an active role in evolution, because Through behavioral adaptations, the effect of selection is manifested in an animal population and the regulation of its structure and numbers is ensured.

Hereditary information from parents to descendants can be transmitted on the basis of direct contacts, through the development of imitative conditioned reflexes and other ways of perceiving and transforming information (the so-called signal heredity). Of particular importance for genetic research is the study of human nervous activity—in normal and pathological conditions. Often mental retardation and mental illnesses have a hereditary etiology associated with genetic metabolic disorders, changes in the number and structure of chromosomes, etc. disorders of the genetic apparatus. Cm . Psychogenetics. (I.V. Ravich-Scherbo.)

Psychological Dictionary. A.V. Petrovsky M.G. Yaroshevsky

Behavioral genetics (behavioral genetics)- a field of knowledge that studies genetic and trace determinants in the variability of animal behavior and psychological characteristics of humans (in the latter case the term is sometimes used human behavioral genetics ).

In Russian, in relation to the study of a person, it is more appropriate to use the term Psychogenetics, since behavior is understood as a set of external actions and actions of a person, and the scope of this concept does not include, for example, sensory thresholds, psychophysiological characteristics (see Differential psychophysiology), formal characteristics of cognitive processes, etc.

Dictionary of psychiatric terms. V.M. Bleikher, I.V. Crook

Neurology. Complete explanatory dictionary. Nikiforov A.S.

no meaning or interpretation of the word

Oxford Dictionary of Psychology

Behavioral genetics- a branch of genetics devoted to the study of patterns of hereditary conditioning of functional manifestations of the activity of the nervous system.

The main task is to describe the mechanisms of implementation of genes in behavioral traits and highlight the influence of the environment on this process. Along with other research methods, the genetic selection method is used here, thanks to which the properties of the nervous system and behavioral characteristics can be purposefully changed. Each heritable behavioral trait usually has a complex polygenic character. Animals from lower levels of the evolutionary ladder (insects, fish, birds) are characterized by low variability in innate, instinctive actions determined by genotype. With evolutionary development, the process of formation of conditioned reflexes becomes increasingly important, and the genotype determines phenotypic variability less and less.

Behavioral genetics, a branch of behavioral science that is based on the laws of genetics and studies the extent and manner in which differences in behavior are determined by hereditary factors. The main methods for studying genetic behavior in experimental animals are selection in combination with inbreeding (inbreeding), with the help of which the mechanisms of inheritance of forms of behavior are studied; in humans, statistical and genealogical analysis in combination with twin and cytogenetic methods. (5).

The dependence of behavior on hereditary factors - gene management and control of behavior - is studied at various levels of the organization of living things: in biocenoses, populations, communities, at the level of the organism, as well as at the physiological (organ, tissue, cell) and molecular levels. Research on the genetics of behavior has significant significance for the study of individual differences in higher nervous activity and identifying the relative role of congenital and individually acquired characteristics of behavior, for explaining the role of genetically determined characteristics of animal behavior in a population (for social animals - in a herd, flock, etc.), as well as for creating experimental models of nervous diseases.

Behavioral genetics is a relatively young field of knowledge, which took shape about half a century ago at the intersection of such disciplines as genetics itself, developmental biology and a complex of behavioral sciences, including psychology, ethology and environmental physiology. The task of this new direction was to study the ontogenesis of a broad class of biological functions of the body, called “behavior” and providing essentially two-way communication between the individual and his surrounding ecological and social environment. The global nature of this task in itself was the reason that the sphere of interests of behavioral genetics soon became involved in such widely separated areas of science and practice as endocrinology and psychiatry, biochemistry and pedagogy, neurophysiology and linguistics, anthropology and breeding of farm animals. In addition, since it has long become obvious that behavior is one of the most important factors in the evolutionary process, the genetics of behavior in recent years has become more and more closely linked with evolutionary teaching, becoming an integral part of modern evolutionary biology.

Genetic analysis of animal behavior

Genetic research in humans has a number of understandable limitations. In this regard, studies of the genetic basis of behavior in animals are of interest. Here you can use selection methods, obtaining inbred lines, modern methods of genetic engineering, selectively turning off certain genes, causing mutations, etc. Inbred lines obtained through long-term inbreeding (at least 20 generations) represent animals identical in genotype, therefore all differences that can be observed among animals of the same line are associated with environmental influences.

Genetics of insect behavior

Let us give an example of genetic analysis of behavior, which is quite often discussed in educational literature. We'll talk about bees and a disease called American larval rot. There is a line of bees that are resistant to this disease because if the disease occurs, the bee larvae will immediately unseal the cell they are in and remove it from the hive. This prevents the spread of the disease, and resistance to it is associated with characteristic behavior! When bees that are resistant to the disease are crossed with those that are not resistant, first generation hybrids (F1) are obtained that do not clean the hives. It is clear from this that the allele or alleles causing this type of behavior are recessive. The first generation F1 hybrids are again crossed with resistant bees (the so-called analytical crossing - with recessive homozygous individuals). As a result, the offspring exhibit four variant phenotypes in a 1:1:1:1 ratio. These are the options:

– bees open the cells and remove the affected larvae;

– open the cells, but do not remove the affected larvae;

– do not open the cells, but remove the affected larvae if the experimenter opens the cell;

– do not open the cells, do not remove the affected larvae.

Thus, it is obvious that this rather complex behavioral act is controlled by genes at only two loci. One allelic gene determines the actions of opening the cell, the other is associated with the removal of the affected larva.

In this case, it is impressive that quite complex actions can be controlled by just one gene.

Fruit flies - Drosophila, which have been a favorite subject of geneticists for many years - have been identified with a huge number of mutations affecting behavior. Yes, mutation dunce leads to disruption of the ability to develop conditioned reflexes. Several mutations are known to disrupt learning in one way or another. It is important that all these defects are associated with impaired metabolism of so-called second messengers (primarily cyclic AMP), which play an important role in intracellular signaling and synaptic plasticity.

There are mutations that lead to high and low sexual activity, to the avoidance of certain odors, changing motor activity, even to the point that there is a mutation that determines how the Drosophila folds its wings - right over left or vice versa.

Sometimes there are examples of very specific behavioral deviations. So, with mutation fru(from fruitless– infertile), the following disturbances in sexual behavior are observed in males: they do not court females, but only court males homozygous for this mutation, and stimulate normal males to court themselves. The result was something like a model for the formation of homosexual behavior.

In general, one gets the impression that most behavioral acts in Drosophila are genetically predetermined in every detail.

Animal learning studies

One of the most important properties of animal behavior is the ability to learn. Animal research provides an opportunity to conduct breeding experiments. Tryon was one of the first to conduct such an experiment on rats. He carried out selection based on the learning ability of animals, which had to find the correct path to feeding placed in a complex 17-dead-end maze. Animals that were good and poorly trained were selected and subsequently crossed only with each other. Regular selection gave a very quick result - starting from the eighth generation, the learning indicators of “smart” and “stupid” rats (the number of erroneous runs in the maze) did not overlap. Selection was carried out until the 22nd generation, as a result of which two groups of rats were obtained - well trained ( bright) and bad – ( dull). Under the same growing and testing conditions, differences between these groups are due only to differences in genotype.

Subsequently, many strains were obtained, especially in mice, differing in their ability to perform various forms of learning. Similar lines were selected for their ability to learn in the T-maze, for learning active and passive avoidance, and swimming in the Morris water test. Sometimes the task an animal performs is quite complex. For example, strains of mice were obtained that were good and bad at learning the food-procuring motor conditioned reflex. The mice were reinforced when they jumped in response to a sound or light stimulus onto different shelves. In this case, some community patterns can be noted:

1) there is usually a large variation of the trait in the source population;

2) Although the selection response can appear very early, and the difference between lines is detected after 2–3 generations, it takes much more generations (about 10–20) for stable significant differences between lines to appear.

The high spread of initial values ​​of the trait and the gradual development of the selection response are evidence of the polygenic nature of the trait. In other words, the manifestation of this trait in the phenotype depends on a relatively large number of genes. The same is true for most mammalian behavioral traits.

There is another problem associated with selection experiments. Selection is carried out when testing a specific task. Naturally, the question arises: to what extent does the ability to solve this problem correlate with the ability for other types of learning? There is no clear answer to this question.

For example, when they began to study in more detail the ability to learn in general on lines of rats obtained by Tryon ( bright And dull), it turned out that those who were well trained ( bright) learn food-procuring behavior faster, and rats dull in turn, demonstrate better performance in defensive reaction tasks. Thus, here the problem of learning can be transferred to the plane of motivational mechanisms. It is known that motivation can have an extremely strong impact on learning outcomes.

It turns out that the rat line bright are more motivated by hunger, while rats dull are more motivated by fear in threatening situations. Just like motivation, the success of learning can be influenced by sensory abilities, the level of motor activity, and the emotionality of animals. Accordingly, genes that influence the activity of these qualities can have an impact on learning.

However, some lineages also show differences in more general learning abilities. So, mouse lines DBA/2J learn better than animal lines C.B.A., which is confirmed in a number of tests: during food reinforcement in the maze, in the shuttle chamber during the development of a conditioned reflex reaction of active avoidance, during operant learning. This means that there are certain genetically determined properties of the nervous system that affect the ability to implement various types of learning. The list of mutations that impair learning and memory in mice is rapidly expanding.

Table 1. Mouse genes localized on certain chromosomes and playing an important role in learning and memory

Differences in memory characteristics were also noted in Tryon's rats, which certainly affected the test results. So, it turned out that rats have lines bright consolidation occurs faster - strengthening of memory traces, their transition into a stable form. You can resort to influences that disrupt short-term memory, for example, using a special form of electric shock that causes amnesia. It turned out that already 75 s after training, electroshock amnesia cannot be induced in rats of the line bright, whereas on the rat line dull The electroshock procedure still has an effect.

Different speeds of consolidation appear to determine differences in the success of forming orientation skills in a maze. What happens if rats line dull will you be given enough time to memorize? Studies have shown that when the intervals between trials were 30 s, rats bright learned much faster than line rats dull, as it should have been. But when the interval was increased to 5 minutes, the difference in learning between the lines decreased significantly. If the rats were given only one trial per day, the learning performance of both strains became identical. The speed of skill acquisition and the speed of consolidation can be determined by different mechanisms!

An important conclusion: selection of learning conditions can reduce or even eliminate differences in genetically determined abilities.

Currently, a number of mouse strains have been obtained that differ sharply in the speed of memory consolidation. There is a line ( C3H/He), in which learning is possible only through continuous training. There is a line ( DBA/2J), in which training, on the contrary, is much more successful when the intervals between individual training sessions increase. And finally, the line (BALB/c) was introduced, for which the nature of the intervals between experimental sessions does not affect the learning results. This approach thus creates unique opportunities for studying memory mechanisms.

Another area of ​​animal research is to elucidate the influence of the environment on the formation of behavioral properties. Let's go back to line rats again bright And dull. You can conduct an experiment to raise these rats in different conditions. One group (control) is grown under normal vivarium conditions. For the other, an “enriched” environment is created - large cells with painted walls, filled with various objects, mirrors, swords, ladders, stairs, tunnels. Finally, the third group is provided with an “impoverished” environment, where the influx of sensory stimuli is severely limited and the possibilities for search and exploratory activity are limited. In graph 1, the enriched environment is designated as “good” conditions, the depleted environment as “bad”. Normal conditions correspond to the control group.

Graph 1. Results of training in a maze of lines of “smart” and “stupid” rats raised in deteriorated, normal and improved conditions. (15).

The results of the control group correspond to expectations - rats of the line bright when learning in a maze, they make much fewer mistakes compared to rats of the line dull. However, for rats raised in an enriched environment, this difference practically disappears, mainly due to a sharp decrease in errors in the “stupid” strain of rats. In the case of rearing in a depleted environment, the difference between the two lines also disappears, and this time mainly due to a sharp increase in the number of errors in the “smart” line of rats.

Here we touch upon a very important problem - the existence of powerful mechanisms of plasticity of the nervous system that are capable of compensating for very significant defects. Numerous studies on raising rats in an enriched environment have shown that relatively quickly - within 25-30 days - very significant morphological differences arise at the level of the cerebral cortex. Animals kept in an enriched environment have a thicker cortex, larger neuron sizes, and a 10–20% increase in the number of dendritic processes per neuron. All this leads to a 20% increase in the number of synapses per neuron. Ultimately, we are talking about billions of new synapses, which dramatically increases the capabilities of the nervous system. Particularly important is the fact that this plasticity potential is maintained almost all the time. Experiments on adult animals led to similar results. Similarly, an enriched environment has an impact on a child’s development.

Video: About the influence of genetics on behavior and character.


Chromosome	Learning and memory

BEHAVIOR GENETICS- a branch of genetics devoted to the study of patterns of hereditary conditioning of functional manifestations of the activity of the nervous system. The main task is to describe the mechanisms of implementation of genes in behavioral traits and highlight the influence of the environment on this process.

Along with other research methods, the genetic selection method is used here, thanks to which the properties of the nervous system and behavioral characteristics can be purposefully changed.

Each heritable behavioral trait usually has a complex polygenic character. Animals from lower levels of the evolutionary ladder (insects, fish, birds) are characterized by low variability in innate, instinctive actions determined by genotype. With evolutionary development, the process of formation of conditioned reflexes becomes increasingly important, and the genotype determines phenotypic variability less and less.

Information important for adaptation is not only acquired in one’s own experience, but can be transmitted from parents to offspring through direct contacts, due to imitative conditioned reflexes.

Data obtained in the genetics of behavior are of particular importance for the study of human nervous activity in pathologies: often mental retardation and mental illnesses are hereditary and associated with genetic disorders.

BEHAVIOR GENETICS(English)

Behavioral genetics) is a section of genetics that studies the patterns of hereditary determination of the structural and functional characteristics of n. With. G. p. allows us to understand the nature of the hereditary transmission of behavioral characteristics; reveal the chain of processes unfolding in ontogenesis leading from genes to traits; isolate the influence of the environment on the formation of behavior within the potential capabilities specified by the genotype.

Using the genetic selection method, the properties of n. s.and behavioral features m.

b. directionally changed. The inheritance of differences in behavioral traits is, as a rule, complex polygenic in nature.

It has been experimentally shown that the species stereotype of animal behavior has a very strict hereditary conditionality.

Low variability of innate, instinctive acts is especially characteristic of animals standing at lower levels of the evolutionary ladder - insects, fish, birds, but even in insects the behavior is m.

b. modified due to the development of temporary connections. Moreover, behavior is not a simple result of evolutionary changes; it plays an active role in evolution, since through behavioral adaptations the effect of selection is manifested in the animal population and the regulation of its structure and numbers is ensured.

Hereditary information from parents to descendants can be transmitted on the basis of direct contacts, through the development of imitative conditioned reflexes and other ways of perceiving and transforming information (i.e.

n. signaling heredity).

Of particular importance for genetic research is the study of human nervous activity—in normal and pathological conditions. Often mental retardation and mental illnesses have a hereditary etiology associated with genetic metabolic disorders, changes in the number and structure of chromosomes, etc.

disorders of the genetic apparatus.

behavioral genetics

See Psychogenetics. (I. V. Ravich-Shcherbo.)

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Lecture 3. 1. Innate forms of behavior

1. Innate forms of behavior

2. Acquired forms of behavior

The adaptation of animals, in the processes of evolution, to relatively constant phenomena and those that are periodically repeated in the external environment, has developed in them genetically fixed, innate forms of behavior.

At the same time, adaptation to fickle, unstable environmental conditions forms in each generation of animals dynamic forms of behavior that are acquired throughout ontogenesis.

Congenital Behaviors

At different stages of evolution, the following innate adaptive reactions can be distinguished: taxis, reflexes and instincts.

Taxis are the simplest form of behavior that determines the interaction of an organism with the external environment in unicellular and multicellular organisms.

Taxis in ethology is called oriented (directed) movement, which is connected with some complex of fixed actions.

For example, when a greylag goose rolls a deflated egg toward the nest, it performs lateral movements that are designed to hold the egg under its beak. These directed movements represent taxis. At the next stages of evolution, the role of taxis sharply decreases and they are replaced by other, more advanced adaptation mechanisms.

Reflexes are also a type of adaptive behavior. In this case, we consider an innate unconditioned reflex reaction, which serves as one of the main types of adaptation in the animal world.

For example, a chicken that has just hatched from an egg begins to peck, and a calf begins to suck.

Instinct (from the Latin “instinctus” - impulse) is a set of innate stereotypical acts of behavior characteristic of individuals of a given species under certain conditions.

Examples include food, imitation, herd, play (in young animals), and migration.

Each such instinct can also include simpler instinctive acts. For example, releasing chicks from the nest, pecking grain, babies sucking milk, and tentatively exploratory reactions.

Instinctive behavior, like all other forms of behavior, has a certain direction - the preservation and development of the organism in conditions characteristic of the life of this species of animal.

According to the teachings of I.P. Pavlov, in the physiological understanding, instincts are chains of complex unconditioned reflexes fixed by evolution, which include compelling and reinforcing reflex links.

In other words, the most complex unconditioned reflexes (for example, nest-building, play, etc.) are represented not by one reflex arc, but by a whole complex of unconditioned reflex reactions.

This complex includes all genetically determined mechanisms necessary for the formation of appropriate acts of behavior: the mechanism of formation of metabolic needs, the mechanism of biological motivations, the mechanism of foresight and evaluation of results, the mechanism of achieving goals (K.V. Sudakov).

Obviously, all mechanisms cannot be formed at the time of birth. Some of them (for example, sexual motivation) are formed in the processes of ontogenesis, as morphofunctional and endocrine systems form and mature.

Coordinated movements of the wings of birds during flight do not immediately arise: this habit depends on learning.

To student I.P. Pavlova to academician L.O. Orbeli has a reasoned concept of postnatal maturation of unconditioned reflexes under the influence and interaction with conditioned ones. For example, building a nest in a rat is an innate chain reflex, but it can be destroyed by raising the rat in a cage with a slatted floor, where the animals’ attempts to collect materials for building a nest have previously ended in failure (P.V.

Simonov). The innate chain reflex of hatching eggs does not manifest itself when chickens are kept in cages.

In our time, the view of the exclusively genetic nature of instincts has changed. Genes cannot determine the course of ontogenesis regardless of the environment.

So, be - what types of behavior are the result of genetic and environmental interactions.

Instinct also needs “training,” which is illustrated by the presence of so-called imprinting.

Instead of the term “instinct,” the expression “innate forms of behavior” is now predominantly used, emphasizing only their relative independence from environmental influences.

In the implementation of acts of behavior based on the innate reactions of animals, the structures of the diencephalon (hypothalamus) and the limbic system play an important role. Thanks to them, behavioral reactions are adaptive, adaptive in nature and are able to maintain biochemical and metabolic homeostasis.

Acquired Behaviors

Acquired forms of behavior include learning and mental activity.

Learning is the process through which life experiences influence the behavior of each individual, and allows animals to develop new adaptive reactions taking into account past experiences, as well as change those reactions that turned out to be non-adaptive.

At the same time, the behavior of animals becomes more flexible and adaptive. As the research of I.P. Pavlov showed, the basis of learning is the formation of conditioned reflexes.

The conditioned reflex is the main form of learning. A conditioned reflex is an adaptive reaction of animals that occurs through the formation of temporary nervous connections between two excitation centers in the cerebral cortex: the center of conditioned and the center of unconditioned stimuli.

The conditioned reflex is a functional unit of activity in the higher parts of the brain.

Two types of conditioned reflexes can be distinguished: the first type is the classical Pavlovian conditioned reflex, the second is the operant (instrumental) conditioned reflex.

Both of them are reproduced in laboratory conditions. In the first case, the animal’s reaction to a conditioned stimulus recreates an unconditioned reflex (secretory or motor), and in the second case, movement, which is a necessary condition for reinforcement. For example, the call is not reinforced with food every time, but only if the animal presses the lever. An example of an instrumental conditioned reflex is the process of drinking water from a drinking bowl.

The animals press the valve with their muzzle, water flows into the drinking bowl and the animals drink. In this reflex there are causal-hereditary relationships, and the fact of unconditional reinforcement depends on the animal itself.

Conditioned reflex learning of both types is associative learning, i.e. such that it arises as a result of the formation of connections in the brain, which can be modified or destroyed when the living conditions of the individual change.

There are also non-associative forms of learning, which include: habituation, latent learning, imitation, trial and error, imprinting, insight.

addictive- the simplest form of behavior - it does not consist in identifying a new reaction, but in losing the one that existed before.

If animals are offered a stimulus that is not accompanied by reinforcement or punishment, then gradually the animals stop responding to it.

For example, birds gradually stop paying attention to a scarecrow that forces them to fly away when it is first placed on the field. Phenomena similar to addiction are found in any group of animals, starting with the simplest, all typical properties of addiction can be found at the level of individual neurons and neuromuscular connections.

Habituation is one of the important processes of adaptation of animal behavior to living conditions. Habituation will also play an important role in the development of behavior in young animals, which are often threatened by various predators (they quickly learn not to respond to foliage when they are moved by the wind and other neutral stimuli).

The innate pecking reaction in newly born chicks is initially directed at any small object, but then habituation to unnecessary objects occurs.

Latent learning according to Thorpe's definition, it is the formation of a connection between indifferent stimuli or situations without explicit reinforcement.

Latent learning, in its natural form, is often the result of animals' exploratory activity in a new situation. In the process of exploring conditions, animals accumulate information about them.

2.10. Behavioral genetics

The life of a small animal or bird when a predator attacks it depends on detailed knowledge of the geography of the area where it lives. Information about the environment can later be used in the processes of searching for food or a sexual partner.

Numerous insects carry out a special “reconnaissance flight” during which they record the position of the site relative to the Sun and the outskirts.

Thus, bees during a reconnaissance flight, which lasts 1-2 minutes, remember the new location of the hives.

Imitation (inheritance)- one of the forms of training.

The learning of species songs by birds is based on imitation. Through imitation, young farm animals learn to master many necessary exercises and habits, for example, the ability to graze. When cows are kept in boxes, a newborn calf, imitating a cow, quickly gets accustomed to eating roughage.

Trial and error method– a complicated reflex in which problems are solved as a result of a blind search.

This type of learning was studied by E. Thorndike through the use of a variety of “problem chests”. The latter were a cage that could be opened from the middle only by pressing a lever or pulling a ring. A cat placed in such a cage makes an attempt to escape; it runs around the cage without stopping until after some time it accidentally tugs at the ring. After the second and third attempts, the cat concentrates its attention on the lever, and as soon as it is locked, it rushes to the ring and fiddles with it.

Trial and error learning is often observed in changes in animal behavior that involve searching for food, storage, or a sexual partner.

As a rule, this process is accompanied by the formation of conditioned reflexes of the first order, since both new stimuli and new behavioral reactions must be remembered.

Trial and error, reliably, is the category that is most suitable and to which the formation of new motor exercises can be attributed. Young mammals and birds, for example, improve the coordination of their movements through training, playing with their parents and among themselves.

Rice. 6. The goslings are watching Konrad Lorenz.

Imprinting was first described by K. Lorenz in 1937 in birds. Imprinting is also observed in sheep, goats, deer, horses and other animals, whose babies are able to move immediately after birth. Imprinting is observed in the reactions of newborn animals following a moving object. Imprinting is a special form of learning that has much in common with conditioned reflex learning, although it is tuned not to individual, but to species characteristics. It is formed only in the early stages of postembryonic development. Thus, in his experiments, Lorenz forced broods of goslings, who mistook him for their mother, to follow him (Fig. 6).

Similar phenomena are observed in mammals. The human-raised lambs follow her and show no curiosity about other sheep. Scott and Filler summarized the results of substantial research in dogs. They found that between three and ten weeks of age, dogs have a sensitive period during which puppies form normal social interactions.

Puppies isolated for more than 14 weeks do not subsequently respond to their relatives, and their behavior is completely abnormal.

Insight- the most important degree of acquired behavior.

This behavior is based on understanding. It occurs predominantly in the most developed representatives of chordates - primates. A classic example of insight in animals is provided by Keller's early experiments on chimpanzees. When several bananas were clinging very high, and the monkeys were unable to reach them, they began to stack boxes one on top of another, or inserted sticks one into another so that they could climb higher and knock the bananas to the ground.

More often, they arrived at such a decision entirely unexpectedly, although they used previous experience of playing with boxes and sticks (latent learning), and the monkeys needed a significant period of trial and error to build a stable pyramid of boxes. Elements of mental activity often appear in the behavior of anthropoid apes and other primates. Numerous dog owners give examples of their dogs doing smart things.

Insight can be seen as a manifestation of the ability to think creatively.

Thinking- the highest form of behavior that dominates in a person. Higher animals have a proven presence of elementary mental activity. An example would be insight. Sometimes, after a series of unsuccessful attempts and a pause, which then comes, animals unexpectedly change the tactics of their behavior and solve the problem. So, in the brains of the animals, an assessment of previously carried out attempts occurred, and adjustments were made to the plan of further actions.

In higher animals, elements of mental activity exist and develop in evolutionary terms. This accounts for the ability of animals to solve complex problems. So, in the animals’ brains an assessment was made of earlier attempts and adjustments were made to the plan for further actions.

In higher animals, elements of mental activity exist and develop in evolutionary terms. This involves animals solving complex problems. The considered forms of complex behavior - learning and thinking - arise at the highest stages of evolution.

Learning becomes dominant in mammals. Their behavior is determined by reactions that are innate and acquired as a result of learning.

Lecture 3

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Variation due to genetic factors

Variation due to genetic factors is complex, but if it is significant and known, it can be used to calculate the possible gain for certain tree characteristics.

Genetic variation can be divided into two main components: additive And non-additive. If we imagine this in statistical terms, then genetic variance consists of additive and non-additive variance components.

The additive component of variance is the variability caused by the combined action of alleles of all gene loci that affect the characteristic. Non-additive genetic variation can in turn be divided into two parts: dominant And epistatic. Dominant variance is caused by the interaction of certain alleles located in one gene locus, while epistatic dispersion is caused by the interaction between genes of different loci.

This concept will be discussed in more detail later.

Here it is enough to note that the additive part is one of the most important in programs for selective improvement of populations.

Non-additive variation can be used in other, more specialized programs that involve making specific crosses or using vegetative propagation for commercial purposes. In most genetic breeding improvement programs, non-additive genetic variation usually receives less attention because the additive portion of the genetic variance can be more easily exploited.

Most characteristics of economic importance are, to one degree or another, under the control of the additive component of genetic variability (V.

Zobel, J. Talbert, 1984). This is important because additive variance can be successfully used in simple breeding systems. The qualitative characteristics of wood, such as density, straightness of the trunk and others, are determined to a greater extent by additive dispersion than growth characteristics.

Although growth performance is controlled to some extent by additive genetic influences, it is also significantly influenced by the nonadditive variance associated with it. Therefore, any breeding program must include testing of the progeny of selected phenotypes to determine the true genetic value of the trees.

The response to selection for characteristics with significant non-additive variance, such as height, is significantly less satisfactory than the response to selection for quality characteristics, which are usually under stricter genetic control of the additive component of variance.

With regard to the characteristics of adaptation, it can be noted that this question has not yet been fully clarified.

However, available evidence favors inheritance of these characteristics in an additive manner. This suggests that any outstanding gains obtained for the improved characteristics of trees that grow satisfactorily in extreme or sub-extreme habitat conditions can be retained.

By selecting trees with outstanding characteristics that grow better in these conditions, and then using their seeds, one can expect to afforest such areas with trees with the desired economically important traits.

Pest resistance includes both additive and non-additive variance depending on the insect and tree species. But usually good results are possible when using the additive part of genetic variability in breeding programs.

The above principles should be used by breeders at the beginning of their work on a particular breeding program.

The first stages of work should involve determining the amount and type of variation in source natural or cultivated populations so that they can then be used in an intelligent manner.

Section 1. General issues of behavioral genetics.

Controlling environmental influences allows for better use of genetic variation.

To identify and use genetically determined variability, certain crossing or mating systems are most often used (matting systems). The type of crossing system within a species has the main influence on the variability of the studied samples.

Cross pollination (outcrossing), which is most characteristic of most species of forest woody plants, as a rule, produces highly variable (heterozygous) populations in genetic terms.

In cross-pollination, different genotypes successfully hybridize with each other, and only a small proportion of crosses occur between female and male organs of the same plant or between closely related individuals.

If the latter occurs, i.e., pollen from a tree or a given genotype pollinates its own female flowers, we speak of self-pollination (selfmg). The same thing happens if pollination occurs between ramets of the same clone.

Even if the ramets (grafts, root suckers, etc.) are separate plants, they are genetically identical.

Therefore, when creating forest seed plantations, care should be taken that grafting trees (ramets) of the same clone are not planted in close proximity to each other.

It should be noted that cross systems support a high degree of genetic variation, while in selfing systems genetic diversity is significantly reduced.

As a rule, growth vigor also decreases significantly when inbreeding occurs, i.e., as if there is a return from the hybrid to the original growth vigor.

This or that degree of relationship is characteristic of natural plantings. For this reason, it is recommended to take only one selected best tree from a stand to create forest seed plantations in one place.

Degrees of relationship can be very diverse. For forest woody plants, little is known about the effects of siblings or other inbreeding.

However, their adverse effects have been well studied in crop plants and are therefore recommended to be avoided. The most common phenomenon is a decrease in sperm production, although there were exceptions when during the mating of half-sibs and even full-sibs such a phenomenon was not observed. But what was common was not only a decrease in seed production, but also a decrease in germination during self-pollination.

When viable seedlings were obtained, they often had poorer growth (Ericsson et al, 1973 - cited by B. Zobel, J. Talbert, 1984). The unfavorable consequences of self-pollination were noted even earlier (A. S. Yablokov, 1965; E. Romeder, G. Shenbach, 1962, etc.; see also chapter).

The results of studying self-pollination in various species of coniferous and deciduous trees showed that the following consequences may occur (B. Zobel, J.

Talbert, 1984; Yu.N. Isakov, V.L. Semerikov, 1997, etc.):

1. No healthy seeds are formed.

2. Seeds are formed, but they do not form shoots.

3. The seeds are viable, but the seedlings are abnormal and often live only a short time and then die.

4. Seedlings survive, but they are small, weak, often with yellowed leaves and slow growing. Some of them can be diagnosed and removed at the nursery stage, before planting in a permanent place.

Seedlings grow more slowly than normal trees, but this is not noticeable enough to remove them at the nursery stage. Their further cultivation is undesirable, since they produce less wood than seedlings obtained from cross-pollination.

6. Seedlings grow as well, and sometimes even better, than those obtained from cross-pollination. Self-pollinating trees, the offspring of which grow as well as those from cross-pollination, are very rare.

All this suggests that when creating forest seed plantations, it is necessary to first study the source material and the possibility of using it in cross-pollination or self-pollination systems.

The use of inbred lines, subsequently cross-crossed, has been proposed as a breeding system.

This method is widely used in agriculture. However, it has been little practiced in breeding programs for forest tree species for several reasons: low seed productivity of self-pollinators, low vigor of inbred offspring, and a significant decrease in wood supply in breeding populations.

In general, based on the materials in this section, it should be noted that genetic variability, a very important aspect of breeding programs, can be significantly increased through intralocus and interlocus interactions, mutations, migrations and other evolutionary factors.

These phenomena will be discussed in more detail in the subsequent presentation.