EPIGENESIS

From Big Medical Encyclopedia

EPIGENESIS (Greek epi-on, later, after + genesis origin, an origin) — the doctrine about germinal development of organisms, according to Krom of fabric and bodies of a germ are consistently formed of unstructured substance of an oosperm. AA. excludes existence in egg and a spermatozoon of any material structures predetermining an ontogeny and signs of an organism. It is opposite to a preformizm (see), to-ry considers development of a germ as simple increase in sizes of completely created microscopic organism preexisting in a sex cell.

Concepts of epigenesis and a preformizm in interpretation of embryonic development existed already during antiquity. So, Aristotle on the basis of the doctrine about dualism of matter and a form created the vitalistic theory, according to a cut of a part of a germ arise in a certain sequence under non-material influence of a men's seed, but in is invisible not to a prebeing-yut the small sizes in «seeds of things», according to prefor-mistsky views antique fi-losofov-materia Anaxogoras, Empedok-les and Demokritos sheets.

In 17 century the epigenic ideas were developed by U. Garvey. It entered the term «epigenesis» in 1651. As the philosophy of development of animals U. Garvey put forward the principle «all from egg» (ex ovo omnia). Development, in his opinion, happens «by addition of the parts separating one from another». For animals, at to-rykh U. Garvey did not find some eggs, it allowed self-generation. As well as Aristotle, U. Garvey considered development from vitalistic positions.

Attempt to develop the mechanical theory E. R. Descartes believing that motive power of development is the «warmth» which is marked out at «fermentation» of two liquids which are mixing up at fertilization undertook.

In 17 — the first half of 18 century the ascendent position in biology is held by a preformizm. The statement of a preformizm was promoted by the early microscopic examinations of germs. Imperfection of the microscopic equipment did not allow to observe initial stages of development of a germ, and detailed studying of germs of animals at late stages gave the grounds to assume preexistence in a germ of all parts of a mature organism. Only in the middle of 18 century under the influence of I. Newton's theory about universal gravitation of Moper-tyui (R. of L. The m of Maupertuis, 1744) and Byuffon (G. L. L. Buffon, 1749) tried to create epigenic concepts on the basis of ideas of an attraction and pushing away of hypothetical particles, or the «organic molecules» which are contained in the semen of a male and female and which are mixing up at fertilization.

At the end of 18 century epigenic concepts drew to themselves attention of biologists in connection with K. F. Wolf's works. Observing early stages of development of a chicken embryo, it described education from allegedly unstructured liquid substances of leaflike plates, to-rye will be transformed to cavities and tubes, originative to various systems of bodies (1759). These researches formed further a basis for creation of the theory of germinal leaves (see). K. F. Wolf considered the reason of development of a germ the special «essential force» providing movement of thin Juices and the dissolved vitelline grains, from to-rykh cells and vessels of a germ, and identified by it with forces of an attraction — pushing away are formed. Thus, «the essential force» had nothing in common with «a vital strength» of supporters of vitalism (see). However further epigenic concepts were widely used by vitalists for confirmation of the idea of «the vital force» as source of development.

Supporters E. there were I. Blyu-menbakh, I. Prokhask and is mute. naturalistic philosophy representatives. From the middle of 19 century after works of X. I. Pandera (1817), K. M. Bera (1827, 1837) and R. Remak (1855) gains development descriptive embryology, and attempts to offer an explanation of ontogenesis (see) both with prefor-mistsky, and from epigenic positions fade into the background.

With emergence at the end of 19 century of development mechanics (see), a subject the cut became the causal analysis of the phenomena of ontogenesis, fight between a preformizm and AA. revives again. Preformistsky positions were upheld by the supporters of the nuclear theory of heredity considering a kernel as the carrier of hereditary properties of organisms (see the Kernel of a cell). Supporters E., as, for example, H. Driesch, more and more came down to vitalism.

In 20 century on the basis of achievements of genetics (see the Geneticist) it was proved that at sex cells there are material structures responsible for transfer to posterity of species and individual characters of parent organisms (see. Chromosomal theory of heredity). Thus, the epigenic ideas were insolvent. Nevertheless wrong attempts to create the epigenic concepts considering development from positions of cybernetics are made.

According to modern representations, the main patterns of development are defined by the genetic information which is contained in DNA of parent sex cells. Formation and growth of an organism both in embryonal, and in the postembryonal period is provided with protein synthesis, DNA coded in structures (see. Genetic code). Regulation of these processes is carried out by interaction of parts of a germ, the nature to-rykh even is completely not found out, and at later stages of ontogenesis — on the basis of humoral, hormonal and nervous bonds. A necessary condition of implementation of internal developments is existence of strictly certain environmental factors.

Thus, the antithesis preformation — epigenesis is removed by modern biology since statements about a full preformirovannost of developments as well as about their absolute epigenetichnost, are wrong. The modern biology considers patterns of developments in unity and interaction of preformirovanny factors (hereditary information) with epigenic factors of ontogenesis. Bibliography: And p t of e r M. Kibernetika

and development, the lane with English, M., 1970; And y-with both N about in and the p A. E., K. F. Wolf and the doctrine about development of organisms (in connection with the general evolution of scientific outlook), M., 1961; Davidson E. Action of genes in a prematurity, the lane with English, M., 1972; It is equal to X. An oogenesis, Accumulation of morphogenetic information, the lane with English, M., 1964. A. E. Gaysinovich.

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