From Big Medical Encyclopedia

DEVELOPMENTAL GENETICS (Greek phaino to show, find - j-of the geneticist) — the section of genetics devoted to a research of formation of ancestral features in the course of ontogenesis i.e. ways from genes — to signs, from a genotype — to a phenotype.

As a result of phenogenetic researches such fundamental provisions in genetics (see) as the netozhdestven-nost of a genotype (see) a phenotype caused by change of manifestation of genes were established (ShM. A gene) depending on an environment of other genes and from conditions of the environment (see Penetrantnost of a gene, Expressivity of a gene). In phenogenetic researches the concept of a reaction norm of a genotype as limit of variability of its manifestation at change of conditions of the environment was formulated, existence at genes of plurality of manifestations (see the Pleiotropia) and conditionality of the same signs is established by different genes (see the Genocopy), and also idea

of a genotype as about uniform complete system, but not the arithmetic sum of genes is formulated. These provisions have fundamental value in modern genetics of an ontogeny of organisms (or just to genetics of development — the term which is forcing out the initial term «developmental genetics» in scientific literature), and also in medical genetics (see), the cut is the large section a pathological developmental genetics of the person.

The term «developmental genetics» was offered in 1918 by the German zoologist and the geneticist Gekker (W. Несkor). He offered also the main method of a research of ways from genes to signs: comparison of normal individuals with mutant at consecutive stages of ontogenesis for the purpose of identification of those moments in development, since to-rykh mutant individuals is found by differences from normal (a so-called method of phenocritical phases). This method remains by the main method F., but in addition to the initial gistoembriologichesky analysis in F. began to apply widely biochemical researches of the developing normal and mutant organisms. Essential results in a research fazosiye-

tsifichnost and tkanespetsifichnost of action of genes, autonomies (or not autonomies) their manifestations in separate cells, fabrics and embryonal rudiments are received on genetic mosaics (see Mosaicism) and chimeras (see) — the organisms consisting of cells of a different genotype. In an ontogeny widely apply to definition of time of action of genes also a method of phenocopies: receiving by means of

the dosed experimental influences (radiation, processing by chemical substances, etc.) the changes imitating manifestations of these or those genes.

Modern F. combines researches at all levels of implementation of genetic information from molecular (see the Transcription, Broadcasting) and before manifestation of action of genetic factors in final morphological, physiological and psychological features of a complete organism.

See also Heredity, Ontogenesis.

Bibliography: Gershenzon S. M.

Fundamentals of modern genetics, Kiev, 1983; B. V. Genetik's Grooms of development of vertebrata, M., 1980; Timofeev-Resovsky N. V. and Ivanov V. I. Some questions of a developmental genetics, in book: Aktualn. vopr. sovr. geneticists, under the editorship of S. I. Alikhanyan, page 114, M., 1966; Timofeev-Ra

sovsky N. V., Ginter E. K. and Ivanov V. I. About some problems and problems of a developmental genetics, in book: Probl. ekspery. biol., under the editorship of D. K. Belyaev, page 186, M., 1977. V. I. Ivanov.