From Big Medical Encyclopedia

GENETICS (the Greek genetikos relating to an origin) — science about heredity and variability of organisms.

Subject and methods of genetics. A subject of studying of G. are two properties of organisms — heredity (see) and variability (see). Heredity — property of organisms to transfer to the next generation features of formation inherent in this organism during ontogenesis of certain lines of a structure and type of a metabolism. Transfer of features of an organism to the next generations is possible only in the course of reproduction or self-reproduction.

Self-reproduction of organisms can be carried out by vegetative reproduction when from parts of a parent individual there is an organism of descendants. So, potatoes, e.g., get divorced generally tubers. At the lowest animals, such as a hydra, some cells reproduce the whole animal. Microorganisms breed preferential by division, some breed budding, and a mold and yeast — by education a dispute. Such precellular forms of the organization of living matter as viruses, breed by a reproduction in a sensory cell where at first there is a separate synthesis virus nucleinic to - you (DNA or RNA) and a squirrel, and then there is their association and formation of virus particles (see. Viruses ). The highest organisms carry out reproduction similar by a syngenesis. New filial generations at a syngenesis result from merge of female and men's sex cells.

Other property of organisms entering an object of research of G. is variability. Variability — the property of live organisms consisting in change of genes and their manifestations in development of an organism i.e. variability is the property opposite to heredity.

Distinguish phenotypical (modification) and genotypic variability.

Phenotypical variability organisms it is connected with the fact that in the course of an ontogeny which is made in certain conditions of the environment change morfol can be observed., fiziol., biochemical, and other features of organisms. However the properties acquired by an organism as a result of such variability are not inherited though limits of fluctuation of a sign (reaction norm) of an organism are defined by his heredity, i.e. set of genes.

Genotypic variability organisms it is caused or change of actually genetic material — mutations (see. Mutation ), or emergence of new combinations of genes — recombination (see). Depending on it genetic variability is subdivided into mutational and rekombinativny (combinative).

Studying of heredity and variability of live systems is conducted at the different levels of the organization of living matter — on molecular, chromosomal, cellular, organismal and population with attraction of methods of related subjects, such as biochemistry, biophysics, immunology, physiology etc. The fact that in G. a large number of specific sections was allocated in independent scientific disciplines, such as molecular, biochemical, fiziol, and medical genetics, an immunogenetics, a developmental genetics, phylogenetics, population genetics, etc. is explained by it. From them are of great importance for medicine a developmental genetics, edges are studied by a role of genes in an ontogeny of an individual; the physiological genetics studying hereditary conditionality of physiology of organisms and influence of environmental factors on it; immunogenetics, pharmacogenetics and genetics of pathogenicity and virulence of microorganisms; the geneticist of populations, finding out laws of heredity and variability in an ecological environment.

The main method of a research of heredity and variability of organisms is genetic analysis (see) which includes a number of private methods. The most informative and specific method of the genetic analysis is clarification of the nature of the sign chosen for such analysis. This method provides system of crossings in a lineage or studying of a family confinedness of the interesting sign for the purpose of the analysis for konomernost of inheritance of separate properties and signs of organisms (see. Inbreeding , Twin method ). The genetic analysis has also private methods of the analysis: recombinational, mutation this, komplementatsionny and population.

Process of material succession in generations of separate cells and organisms is studied with the help tsitol. a method which in combination with genetic received the name of a cytogenetic method of studying of heredity. After opening of a genetic role nucleinic to - the t successfully develops a method of the molecular analysis of structure and functioning of a gene. The phenogenetic method provides studying of action of a gene and its manifestation in an ontogeny of an organism. Such receptions as transplantation of hereditarily various fabrics, change of kernels from one cell in another etc. are for this purpose used. The analysis of such genetic phenomena is kept also with attraction of the latest methods of various industries of natural sciences, in particular biochemistry, however all used methods of other disciplines for G. are only auxiliary to the main method — the genetic analysis.

Main stages and directions of development of genetics. Various hypotheses of the nature of heredity and variability expressed at a dawn of culture of mankind. Observations of the person over by itself, and also the results of experiences received at animal husbandry and cultivation of plants formed a basis for them. Already in those days the person made a certain selection, i.e. left for further reproduction only of those animals or those plants which had qualities, valuable to it. Thanks to such primitive selection the person managed to create a large number of types of various domestic animals and cultural plants - the First compositions on heredity and variability appeared only in 17 century when R. Camerarius in 1694 published «Notes about the field at plants» where drew a conclusion that plants, as well as animals, have sexual differentiation. He also suggested that pollination of a plant of one look pollen of other look can lead to emergence of new forms. At the beginning of 18 century began to receive hybrids and to describe them. The early scientific research on hybridization was carried out by J. Kolreuter in the 60th 18 century. It showed that as a fatherly or maternal plant any of parent types Since during the crossing in both directions identical hybrids turn out can be used, i.e. in transfer of heredity play an identical role both pollen, and a seedbud.

Further vegetable hybrids for the purpose of detection of patterns of emergence in them parent signs many researchers — Th.Knight, Naudin researched (Ch. Naudin), etc. Their observations could not become base for formation of science yet, however along with rapid development of breeding livestock production, and also crop production and seed farming in the second half of 19 century they excited keen interest in the analysis of the phenomena of heredity.

Especially strongly development of science about heredity and variability was promoted by Ch.'s doctrine of Darwin (1859) about the origin of species, a cut enriched biology with a historical method of a research of evolution of organisms. Darwin put a lot of effort for studying of the phenomena of heredity and variability and though he did not manage to determine consistent patterns of heredity, he nevertheless collected a large number of the facts, drew a number of the correct conclusions on their basis and proved that types are changeable and that they came from other types which differed from extant.

Fundamental laws of G. were open and formulated chesh. the scientist Mr. Mendel experimenting with various grades of peas (1865). G. Mendel stated results of the researches in the become classical book «Experiences with Vegetable Hybrids» published in 1866. For experiments on hybridization it used two grades of peas which differed in a form of seeds or coloring of flowers. It allowed G. Mendel to develop practically methods of the genetic analysis of inheritance of separate signs and to establish essentially important situation saying that signs are defined by the separate hereditary factors which are transmitted through sex cells and that separate signs of organisms during the crossing do not disappear, and remain in posterity (see. Mendel laws ). Though G. Mendel knew nothing about location of hereditary factors in a cell, about their chemical nature and the mechanism of influence on this or that sign of an organism, nevertheless its doctrine about hereditary factors as units of heredity formed the basis of the theory of a gene (see. Gene ).

However basic results of experiences of G. Mendel were understood by biologists only in 1900 when a goal. botanist of X. de Fris and almost along with it is mute. botanist Korrens (S. Correns) and avstr. uchetsy E. Tschermak for the second time opened laws of inheritance of characters. From now on rapid development of G. approving the principles of discretization in the phenomena of inheritance began, and 1900 it is considered to be official date of birth

of G. V of 1906 on the III International congress on hybridization according to W. Bateson's proposal the science studying heredity and variability it was called genetics, and Mendelian unit of heredity according to W. Johannsen's proposal soon received the name «gene» (1909).

In 1901 X. de Fris formulated the theory of mutations saying that hereditary properties and signs of organisms change in steps, i.e. as a result of mutations (see. Mutation ). It was soon established that hereditary factors are connected with chromosomes, and in 1911 T. Morgan, Bridzhiz (S. V. of Bridges), Meller (N. of J. Muller), A. H. Sturtevant, etc. created the chromosomal theory of heredity (see) and experimentally proved that the main carriers of genes are chromosomes and that genes are located in a chromosome in a linear order (see. Chromosomes ).

Creation of the chromosomal theory made the central theory of G. the materialistic concept of a gene. Being guided by this theory, geneticists in 30 — the 50th 20 century had an opportunity to conduct researches which results had huge basic value.

In 1926 — 1929 S. S. Chetverikov with sotr. carried out by the first the experimental genetic analysis of populations of a drosophila, than laid the foundation of the modern direction in population and evolutionary. Big contribution to development population genetics (see) made amyor. scientist S. Wright and English scientists Fischer (R. Fisher, 1890 — 1962) and Haldane (J. Century of S. Haldane, 1892 — 1964), put in 20 — the 30th of a basis of a genetiko-mathematical method and the genetic theory of selection. For development of populations by experimental G. the Soviet scientists N. P. Dubinin, D. D. Romashov and N. V. Timofeev-Resovsky made much.

In development of genetic bases of selection the large contribution was made by the Soviet geneticists M. F. Ivanov, A.S. Serebrovsky, B. I. Vasin, P. I. Kuleshov, etc.

In 1929 — 1934 N. P. Dubinin, A.S. Serebrovsky, etc. for the first time put forward and experimentally confirmed the idea about a drobimost of a gene, according to a cut the gene represents a complex system with the special internal organization and with falsehood of functions. In 1943 experiments by definition of a position effect of genes at a drosophila N. P. Dubinin and B. N. Sidorov proved more exhaustively that the normal dominant gene as a result of change of a gene environment in a chromosome loses such important property as dominance (see). The open phenomenon demonstrated that action of a gene is in connection with its situation in a chromosome.

In 1925 A. Nadson and G. S. Filippov on yeast and in 1927 Meller on a drosophila received hereditary changes (mutations) under the influence of X-ray. Almost along with Meller radiation mutations at plants were received by L. J. Stadler. Thus, it was for the first time experimental variability of genes under the influence of environmental factors is proved.

Opening of a mutagenesis under the influence of chemical substances on the value was equal to opening of mutational action of radiation exposure. It was established that many chemical substances sharply raise a mutation rate in comparison with a spontaneous background. I. A. Rappoport opened powerful mutagen effect of ethylene imine (1946), a cut afterwards was widely used for creation of highly productive strains of producers of antibiotics (S. I. Alikhanyan, S. Yu. Golding, etc., 1967).

In 1941 Mr. G. W. Beadle and E. L. Tatum in the USA received biochemical, mutations at neurodisputes that laid the foundation for studying of mechanisms of genetic control of metabolism of a cell.

A basic stage in development of the direction which became further central during creation molecular genetics (see), N. K. Koltsov's speech «Physicochemical fundamentals of biology» was, to-ruyu it said at the III All-Russian congress of anatomists, zoologists and histologists in 1927 N. K. Koltsov stated and developed a look which was the basis for all molecular biology later, namely that the essence of the phenomena of heredity should be looked for in molecular structures of those substances in a cell which are carriers of these properties. It developed the matrix theory of an autoreproduktion of chromosomes, considering that the initial chromosome is a matrix (template) for; daughter chromosome. Specific mechanisms of reproduction of hereditary molecules were others, however the ideological principles of modern ideas of a reproduction of molecules were created by N. K. Koltsov.

The large contribution to genetics was made in 1920 — 1940 by N. I. Vavilov. The evolutionary origin of an orientation of mutations at related forms is shown in the law of ranks of homologous variability and the centers of a gene pool offered them. All this allowed N. I. Vavilov (1936) to prove such approach to problems of a look which allowed to present a look as a complex system in certain conditions of the environment. N. I. Vavilov creatively proved the doctrine about genetic bases of selection (see. Artificial selection ).

In the field of medical G. our country in the 30th 20 century came to the forefront in the world. In particular it was shown in the area G. of nervous diseases which studying probodatsya under the leadership of S. N. Davidenkov. It found the signs connected with incomplete manifestation of genes and their heterozygosity at various nervous diseases. Davidenkov described a large number of the hereditary factors korrelyativno influencing a nervous system. He characterized and classified more than hundred diseases of c. the N of page also made the first attempt to generalize and submit data on evolution of a gene pool of mankind.

Thus, by 40th 20 century G. as science achieved considerable success, and the Soviet G. took the leading place in world science about heredity and variability. However it was still considered to be that a material basis of a gene is protein. In 1944 Mr. of Avery (O. T. Avery), Mac-Laud (G. M of MacLeod) and IAC Carti (M. of McCarty) proved that the substance responsible for transfer of ancestral features at Diplococcus pneumoniae, is deoxyribonucleic to - that (DNA). It was an incentive for studying chemical, physical. and genetic essence of DNA, beginning of the period molecular. After opening transformations (see) a big role played opening of sexual process at bacteria in G.'s development — conjugation (see. Conjugation at bacteria ) and abilities of phages to transfer genetic material from one bacteria to others — so-called. transductions (see). Exactly from now on geneticists begin to work at the organisms having relative genetic simplicity i.e. at bacteria and at bacterial viruses.

An exclusive event in G. was interpretation of structure of molecule DNA by J. Watson and T. Shout (1953). This opening made possible disclosure of a secret genetic code (see). Thanks to interpretation of a genetic code it was solved the mechanism of consecutive connection of the remains of amino acids in molecules of polypeptides under construction and proteins. It was followed by other opening: synthesis of a genome of a phage of X174 (A. Kornberg et al., 1967), allocation from E. coli lac-оперона [J.Shapiro et al., 1969], allocation of the gene managing synthesis of ribosomalny RNA [Colli, Oishi and soavt., 1970; Spadari and soavt., 1971], allocation of the gene controlling synthesis tirozinovy acceptor RNA [Marks and soavt., 1971], allocation of genes of the II area of a phage of T4 [Goldberg (I. N of Goldberg, 1969], chemical synthesis of a gene alanine acceptor RNA yeast, consisting of 77 nucleotides (X. Koran, etc., 1968).

Creation of the concept about transfer of genetic information was the following stage of development of molecular G. This concept received the name of «the central dogma of molecular biology». Its contents came down to the fact that transfer of genetic information goes only in one direction: DNA -> IRNK —> protein. Meanwhile by Temin's researches (H. Temin, 1970) and Baltimore (D. Baltimore, 1970) it was established that the tumoral RNA-containing viruses possess enzyme, under influence to-rogo virus RNA becomes a matrix for synthesis of DNA, i.e. the return transfer of genetic information (reverse transcription) from molecules RNA on DNA is carried out. This enzyme received the name «return transcriptase». Opening of this phenomenon has deep methodological value since demonstrates that though the genetic code is ciphered in molecules DNA or RNA, but the essence of heredity is not limited to it, and consists in interaction of proteins and nucleinic to - t. It is confirmed also by what all genetic processes connected with DNA demand for the implementation of availability of enzymes, i.e. proteins. In particular, such processes as replication, a recombination, a mutation, a reparation damaged chemical and physical. factors of molecule DNA, demand participation of the corresponding enzymes, i.e. the essence of heredity consists in interaction of DNA, RNA and protein in a cell.

Along with studying of chromosomal factors of heredity great theoretical value has clarification of a role of so-called extra chromosomal factors of heredity at bacteria — episomes. To episomes temperate backteriophages, sexual factors, factors of multiple resistance belong to medicinal substances and bakteriotsinogenny factors (see. Episomes ). For medical geneticists the problem of episomes represents interest since the experimental data testimonial of the fact that the genes defining virulence of bacteria have not only the chromosomal nature are obtained, but often are also a part of episomes. It is enough to note that pathogenic properties of some bacteria as, e.g., the causative agent of diphtheria, botulism, and also pathogenic stafilokokk and streptococci, are connected with lysogenization their bacteriophages having the genes determining synthesis of toxic products as a part of DNA. Allocation of such lysogenic bacteriums from mix with prophases led to emergence of avirulent cultures.

Thus, history of development of G. can be divided into three stages. The first stage — the period of classical genetics (1900 — 1930) caused by creation of the theory of discrete heredity (mendelism). The second stage (1930 — 1953) is characterized by deepening of the principles of classical G., but at the same time and review of a number of its provisions. At this time possibilities of artificial receiving mutations were open, complex structure of a gene is revealed and proved, established that DNA, but not protein, is the material carrier heredities (see).

The third stage of development of G. can be considered the period of its development since 1953 when the genetic role of molecules DNA was almost completely revealed and its structure is revealed. Further researches in this area, and especially in the field of DNA-dependent synthesis of protein, continuous connected G. with biochemistry.

Since 1953 especially intensively there is G.'s penetration into interdisciplinary sciences, in particular of particular importance is biochemical genetics (see) and medical genetics (see).

Consecutive use of the principle «one gene — one enzyme» (i.e. one gene is responsible for synthesis of one enzyme) gave the chance to find out origins of a number of hereditary defects of exchange from the person and to establish what disturbance of synthesis of enzyme or substance the ketonuria, an alkaptonuria, a tyrosinosis, albinism, hemophilia, various forms of hereditary cretinism, drepanocytic anemia and other hemoglobinopathies etc. causes such diseases of the person as phenyl.

The doctrine about chromosomal diseases of the person develops in the same period. In 1956 for the first time it was succeeded to define true diploid chromosome number of the person (46), and in 1959 to establish that at a Down syndrome in all cells of a body of the person the excess 21st chromosome therefore the conclusion was drawn that this disease is caused by not discrepancy of couples of chromosomes 21 at formation of gametes is found (usually ova).

Almost it was at the same time established that three forms of congenital anomalies of a floor (Klaynfelter's syndrome, Shereshevsky's syndrome — Turner and the anomaly conducting to mental retardation and infertility) are caused by disturbance of set of gonosomes. It became clear that all these three forms result from not discrepancy of gonosomes at formation of a gamete. Along with these typical chromosomal diseases more than 200 various syndromes caused by more difficult types of not discrepancy of chromosomes are described.

Opening of a role of chromosomes in developing of many congenital anomalies and hereditary diseases led to rapid development cytogenetics (see) and its strong communication with medicine.

The cytogenetics promptly gets into oncology. Value of chromosomal anomalies of somatic cells and somatic selection in development of malignant tumors is found out. It is established that tumor cells have, as a rule, abnormal chromosome complexs and that during carcinogenesis there is an intensive competition between cells of a different karyotype and a genotype (see. Genetics of somatic cells ).

Identification of a large number of the hereditary diseases of endocrine system which are a consequence of abnormal enrollment of gonosomes led to close contact between G. and endocrinology.

The increasing penetration of G. into immunology and especially in radiobiology is noted. The experimental data allowing to draw a conclusion that damage of hereditary elements of a considerable part of cells of an organism is the cornerstone of a radial illness are obtained.

Rapid development of G. in the 60th 20 century could not but exert impacts on a number of disciplines, adjacent to it. Intensive operation of natural selection concerning genovariations, some types of chromosomal reorganizations was shown. All this led to evolutionary G.'s creation (see. Theory of evolution ), studying distribution and fixing of a number of mutations during natural selection and at speciation. By evolutionary G.'s methods (in experiences with microorganisms and insects) it was shown that hereditary adaptation to the environment is made not as a result of adequate change of hereditary properties of an individual organism under the influence of an external factor, and as a result of the directed selection of the hereditary changes arising irrespective of a factor of the environment to Krom there is adaptation.

Intensively the doctrine about the balanced hereditary polymorphism of the person consisting in existence in human populations not less than two alleles of the same gene, and both alleles (and sometimes develops and many alleles) meet the frequency excluding distribution of less frequent allele without participation of intensive selection. So, in addition to 15 systems of antigens of erythrocytes (blood groups And, In, 0, NH, a Rhesus factor etc.), the large number of groups of leukocytes and thrombocytes, proteins of plasma, various enzymes, hereditary systems of allocation and exchange, etc. opens. Detection of sharp hereditary distinctions in reaction to some medicines already led to rapid development of brand new area of medical G. — pharmacogenetics (see). An increasing number of data that this hereditary biochemical, heterogeneity of mankind within its norm arises under the influence of selection collects, and the factor which in most cases is selecting were microbic infections. It was confirmed by distinction of hereditary options of hemoglobin, the raised susceptibility of people with a blood group And to smallpox etc.

Thus, the genetics studies and analyzes the main biol, processes at molecular level (biosynthesis, autosintez DNA and a gene), cellular (fiziol., cytogenetics), individual (G. of individual distinctions, physiology of reproduction) and population (G. of populations), opens mechanisms of individual and phylogenetic development.

Establishes connection with cytology, selection, theory of evolution, a systematics, experimental embryology, biochemistry, biophysics, cybernetics, medicine, microbiology, immunology, radiobiology. Enriches each of these sciences of G. with the methods and achievements, becoming their integral part, and at the same time itself is enriched with data and methods of these disciplines. It does G. by the most important tool of knowledge of essence of life. Having revealed many secrets of the nature, G. made thereby an invaluable contribution to development of materialistic natural sciences.

G. are faced by the important tasks following from already determined general consistent patterns of heredity and variability. Studying of the mechanism of change of a gene, reproduction of genes and chromosomes, action of genes and monitoring by them of elementary reactions and formation of difficult signs and properties of an organism in general, interrelation of processes of hereditary variability and selection in development of the organic nature first of all concerns to them. Besides, G. are faced also by closer tasks which permission is necessary for practice, especially for a wedge, medicine.

The geneticist and the practician

G. as the science standing on a first line of a scientific and technological revolution, being guided by the laws opened by it, makes an essential contribution to many industries of human activity. Thanks to G.'s progress the foundation mikrobiol is laid, the industries, value a cut everything increases. Production of antibiotics, amino acids and other substances is based on use of radiation and chemical mutants of bacteria, viruses, etc.

G.'s progress of plants promoted sharp increase in productivity of all main pages - x. cultures: wheat, sunflower, corn, sugar beet, etc. In general work of geneticists and selectors allowed to improve seriously production of food resources on all planet.

Especially G. is important for the solution of many medical problems, especially in fight against infectious and hereditary diseases. Only thanks to G.'s progress of microorganisms producers of antibiotics which efficiency of synthesis in hundreds and thousands times more, than at wild strains of these microbes are received.

Special value for medical practice had detection by the Japanese researchers of Watanabe (T. Watanabe, 1959) and Akiba (T. Akiba, 1959) at bacteria of factors of multiple resistance (R-fakto-ditch) to medicinal substances.

Opening R-factors (see), studying of their structure, detection in their structure of the genes controlling synthesis of the enzymes destroying medicines gave the chance to find out origins of so eurysynusic phenomenon as medicinal substances resistance of many species of pathogenic microbes (see. Medicinal stability of microorganisms ). Difficulties of fight against the infectious diseases caused by the activators possessing R-factors dictate need of development of the measures interfering their distribution that is possible only during the use of the latest developments in the area G. of microorganisms.

Use of achievements of G. in fight against hereditary diseases of the person is especially important for medicine (see. Medical genetics ).

Three main modes of inheritance are characteristic of hereditary diseases depending on where the changed gene (an autosome or a gonosome) and what its relationship with a normal allele (dominant or recessive mutation) is localized: autosomal and dominant, autosomal and recessive and linked to a floor, or limited by a floor (see. Inheritance ). At the diseases inherited on autosomal dominantly type, sick boys and girls are born with an identical frequency since the mutational gene is shown already in a heterozygous state. At the diseases inherited on autosomal recessively type, the mutational gene is shown only in a homozygous state. At diseases which transfer is limited to a floor (H-chromosomal type) actions of a mutational gene are shown only at men, i.e. at a heterogametic sex (hemophilia And, color-blindness, etc.).

Further deepening of ideas of the nature of inheritance of various diseases and especially further studying of influence of various environmental factors on manifestation of mutational genes allows to plan more clearly ways of prevention, diagnosis and treatment hereditary diseases (see). Development mikrobiol, and other express methods of identification of hereditary diseases of exchange in this respect is of great importance. Establishment etiol, a factor of a disease opens ways of treatment: an exception (or restriction) from among food stuffs of those connections which metabolism in an organism is broken because of blocking of any enzyme; replacement therapy by this enzyme. In prevention of hereditary diseases the huge part is assigned to system medicogenetic consultations (see) which value everything increases, especially during development of methods of definition of a heterozygous carriage and establishment of the nature of distribution and frequency of gene and chromosomal hereditary diseases. Timely establishment of the hereditary nature of a disease and a mode of inheritance allows to develop more successfully methods of the prevention of a course of a disease, especially at early age, and its treatments.

Particular interest and value for medicine is represented by quickly developing field of genetics which received the name of genetic engineering (see. Genetic engineering , Gene therapy ), the essence a cut consists in introduction to a genome of the genetic material changing hereditary properties of an organism. Selection and allocation of genes and, with another — introduction of these genes to genomes of cells of the chosen organisms are necessary for implementation of genetic engineering, on the one hand.

Much attention is paid to studying of the mechanism of a reparation of damages of a cellular genome. The researches in the beginning conducted on microorganisms showed that bacterial cells possess special systems which recover the injuries of genetic material (DNA) received at action of a row chemical and physical. agents, also provide relative stability of cells to action of these agents. The reparation of damage of DNA is carried out with the participation of a number of the enzymes determined by certain genes (see. Reparation of genetic damages ). The Repariruyushchy systems for the first time opened at bacteria are inherent as well in cells of the person and animals. E.g., cells of Xeroderma pigmentosum (the hereditary disease of the person leading to a carcinoma cutaneum) are much more sensitive to UF-radiation, than normal cells since they cannot recover the sites of DNA damaged by ultraviolet rays due to the lack of the corresponding fermental systems. At the same time cells of cancer of eyes of cattle are capable to a reparation of the damaged DNA since they contain enzymes necessary for this purpose.

Existence of the systems controlling DNA repair has obshchebiol. value. If the mechanism of elimination of disturbance of structures of DNA was absent, then the organism would be absolutely defenseless, and the chemotherapy and medicinal therapy would be impossible. Intensively conducted researches on studying of the mechanism of formation of enzymes of repariruyushchy systems are very perspective.

Modern G., despite already achieved considerable success in studying of molecular bases of heredity, continues to develop at the molecular, submolecular, cellular, fabric, organismal and population levels and became key science of modern biology, closely connected in the practical relation with agriculture, medicine, bioastronautics, theory of the biosphere, the theory of evolution, anthropology and the general doctrine about the person.

G.'s development decides by its dialectic interaction on physics, chemistry, mathematics and cytology. Approaches understanding of heredity, being guided by the principles of integration, integrity of its organization, and it brings closer it to knowledge of essence of life, gives qualitatively new methods for management of it that allowed to call this stage of development of G. synthetic. In general G., as well as other sciences, in 60 — the 70th 20 century pass from spontaneous detection of dialectics in fundamental laws of life to conscious use of materialistic dialectics.

The main centers of genetic researches and press organs

In the USSR the main centers of researches on G. are: Ying t of the general genetics of Academy of Sciences of the USSR, Ying t of developmental biology of Academy of Sciences of the USSR, Ying t of molecular biology of Academy of Sciences of the USSR, Radio biological department Ying-that atomic energy of Academy of Sciences of the USSR, Ying t of medical genetics of the USSR Academy of Medical Sciences, the Award of the Labour Red Banner Ying t of epidemiology and microbiology of a name of the honorary academician N. F. Gamalei of the USSR Academy of Medical Sciences, Ying t of virology of D. I. Ivanovsky of the USSR Academy of Medical Sciences. Researches in the field of medical G. are conducted in many a wedge, in-ta of the USSR Academy of Medical Sciences and M3 of the USSR and federal republics, in Ying-those cytology and genetics of the Siberian department of Academy of Sciences of the USSR (Novosibirsk), Ying-those geneticists and cytology of AN of BSSR (Minsk), Ying-those cytology of Academy of Sciences of the USSR (Leningrad), Ying-those geneticists and selections of industrial microorganisms of Glavmikrobioprom (Moscow), the Sector of molecular biology and genetics of AN of USSR (Kiev), and also at the relevant departments MSU, I LIE also other high fur boots and medical higher education institutions of the country.

In 1965 it is organized All-Union about-in geneticists and selectors of N. I. Vavilov with departments on places. Teach in all high fur boots, medical and page - x. higher education institutions of the USSR.

Genetic researches are intensively conducted in other socialist countries. It is developed in Great Britain, India, Italy, the USA, France, Germany, Switzerland, Sweden, Japan, etc. Each 5 years gather the international congresses till.

The main publications which are systematically publishing articles according to G. are: Genetika magazine of Academy of Sciences of the USSR, Cytology and Genetics magazine of AN of USSR. Articles according to G. print also many biol, and medical magazines, e.g. «Cytology», «Radiobiology», «Molecular biology».

Abroad articles according to G. are printed in «Annual Review of Genetics» * by «Theoretical and Applied Genetics», «Biochemical Genetics», «Molecular and General Genetics»,> «Heredity» «Mutation Research», «Genetics», «Hereditas», «Journal of Heredity», «Canadian Journal of Genetics and Cytology», «Japanese Journal of Genetics», «Genetica Polonica», «Indian Journal of Genetics and Plant Breeding».

See also Genetics of the person .

Bibliography: Vavilov H. I. Chosen compositions, Genetika and selection, M., 1966, bibliogr.; Dubinina. P. Horizons of genetics, M., 1970, bibliogr.; it, General genetics, M., 1976, bibliogr.; Dubinina. Item and Glem-botsky Ya. L. Genetika of populations and selection, M., 1967, bibliogr *; History of biology since the beginning of the 20th century up to now, under the editorship of L. Ya. Blyakher, M., 1975, bibliogr.; Classics of the Soviet genetics 1920 — 1940, under the editorship of P. M. Zhukovskogo, L., 1968; L about and sh e in M. E. Genetik, L., 1967, bibliogr.; Medvedev. N. Prakticheskaya of the geneticist, M., 1968, bibliogr.; Mendel G. Experiences over vegetable hybrids, M., 1965, bibliogr.; Morgan T. The chosen works on genetics, the lane with English, M. — L., 1937, bibliogr.; P of IS of ER R. and Mikhaelis A. Genetichesky and the cytogenetic dictionary, lane with it., M., 1967, bibliogr.; Sedzher R. and Rein F. Cytologic and chemical bases of heredity, the lane with English, M., 1964.

Periodicals — Genetics, M., since 1965; Achievements of modern genetics, M., since 1967; Cytology and genetics, Kiev, since 1967; Annual Review of Genetics, Palo Alto, since 1967; Biochemical Genetics, N. Y., since 1967; Genetics, Brooklyn — N.Y., since 1916; Hereditas, Lund, since 1920; Journal of Heredity, Washington, since 1910; Molecular and General Genetics, V., since 1908; Mutation Research, Amsterdam, since 1964; Theoretical and Applied Genetisa, V., since 1929.

H. P. Dubinin, I. I. Oleynik.