the branch of genetics that studies the ways in which hereditary information is manifested during the course of individual development. Phenogenetics may also be defined as the branch of genetics that studies the ways in which the genotype is manifested in the phenotype; according to the Soviet biologist B. L. Astaurov, phenogenetics studies the genotype’s fulfillment reaction. The ways in which the genotype is manifested in the phenotype may be defined as the mechanisms of action and interaction of genes and their products with one another and with internal and external environmental factors during the course of an organism’s development.
The term “phenogenetics” was introduced in 1918 by the German zoologist and geneticist V. Haecker. To Haecker, the primary task of phenogenetics was the ascertaining of phenocritical periods, that is, those developmental stages when differences between normal and mutant individuals may be detected and the locus and mechanism of gene action may be determined from these differences. Some variants of Haecker’s approach are used in modern phenogenetics.
The study of the laws that govern the final manifestation of those genes which control morphological characters was an important stage in the development of phenogenetics. The concepts of penetrance and of the expressivity of genes were introduced by N. V. Timofeev-Resovskii in 1927, and the concept of the area of gene action, by P. F. Rokitskii in 1929. These concepts, which were introduced in order to discover quantitative and qualitative characteristics in the variability with which such genes are manifested, are now widely used in both general and applied phenogenetics, and particularly in medical phenogenetics. Also relevant to phenogenetics are the long-term studies of the German biologist R. Goldschmidt on the genetic and hormonal mechanisms that regulate the development of primary and secondary sexual characteristics in animals, although Goldschmidt considered his research to be within the field of physiological genetics.
Phenogenetics devotes much attention to the study of genetic mosaics—organisms composed of cells of different genotypes. Genetic mosaics can be obtained by subjecting embryos to various types of external influence, generally irradiation, or by combining embryonic cells from individuals of different genotypes. The research conducted by the American geneticists C. Stern and B. Mintz between 1940 and the 1970’s on the relative distribution of genetically marked cells in the tissues and organs of mosaics, as well as on the mutual influence of genetically differing cells in the same organism, has facilitated the study of the cellular and genetic bases of histogenesis and organogenesis. These two processes are the most important stages in the individual development (ontogeny) of higher multicellular organisms.
Also of importance in phenogenetics is the study of the genetic mechanisms that regulate individual development. This area of study is often considered to be an independent discipline, that of developmental genetics. Recent research has established the role of DNA as genetic material, has discovered the mechanism of protein synthesis, and has deciphered the genetic code. These achievements have made it possible to conduct research on phenogenetics at the molecular level and at the level of the primary products of genes and their interaction with one another. Modern phenogenetics is thus an extensive discipline, studying the molecular mechanisms of gene action, the regulation of this action, and the interaction of genes and their products in the final manifestations of genetic information. Phenogenetics also studies the role of heredity and environment in the formation of individual characters.
REFERENCESRokitskii, P. F. “Oblasti deistviia genov.” In Trudy Vses. s”ezda po genetike, selektsii, semenovodstvu i plemennomu zhivotnovodstvu, vol. 2. Leningrad, 1930.
Timofeev-Resovskii, N. V., and V. I. Ivanov. “Nekotorye voprosy fenogenetiki.” In the collection Aktual’nye voprosy sovremennoi genetiki. Moscow, 1966.
Koniukhov, B. V. Biologicheskoe modelirovanie nasledstvennykh boleznei cheloveka. Moscow, 1969.
Haecker, V. “Aufgaben und Ergebnisse der Phänogenetik.” In Bibliographia genetica. The Hague, 1925.
Goldschmidt, R. Physiological Genetics. New York-London, 1938.
Timofeeff-Ressovsky, N. W. “Allgemeine Erscheinungen der Genmanifestierung.” In Handbuch der Erbbiologie des Menschen, vol. 1. Berlin, 1940.
Stern, C. Genetic Mosaics and Other Essays. Cambridge, Mass., 1968.
Mintz, B. “Allophenic Mice of Multi-embryo Origin.” In Methods in Mammalian Embryology. San Francisco, 1971.
V. I. IVANOV