Genetics and American society : a historical appraisal / Kenneth M. Ludmerer.

  • Kenneth Ludmerer
Date:
[1972]
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Genetics and American society : a historical appraisal / Kenneth M. Ludmerer. Source: Wellcome Collection.

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    76 A Decade of Change: 1914-1924 environmental influences. He discovered that inherited variations could be small, environmentally produced variations large, and that the two could be distinguished from each other only by the use of breeding tests. To interpret his observations he introduced the terms genotype, the genetic makeup of the organism, and phenotype, the observed character pro¬ duced by the genes with the environment. These investigations, to the dismay of extreme hereditarians, clearly demonstrated the sensitivity of genes to environmental influences; they showed that development is deter¬ mined not by heredity alone but by the interaction of heredity and en¬ vironment.^ In 1908 G. H. Hardy of England and Wilhelm Weinberg of Germany derived independently what is known today as the Hardy-Weinberg law, the foundation of modern population genetics. This law gave a mathemati¬ cal treatment of gene equilibrium in human populations.^ It imphed, among other things, that the ehmination of a trait from a population is an extraordinarily long and complex process, thereby belying eugenicists' claim that breeding for or against a particular trait is an easy task. While this principle was not generally appreciated or recognized for the first ten years after its initial exposition, it served as the basis of the important work in population genetics which occurred thereafter, and thus it ulti¬ mately estabhshed the foundation of one of the most convincing scientific repudiations of eugenicists' scientific world view. Between 1910 and 1913 the American geneticists Edward M. East and Rolhns A. Emerson accumulated crucial evidence which disproved the notion that most, if not all, traits are determined by single genes. Studying 2. See W. Johannsen, От Arvelighed i Samfund og i rene Linier. Oversigt over det Kgl. danske videnskabernes selskabs forhandlinger #3 forelagt i modet den 6 Feh. 1903\ and Johannsen, Elemente der Exakten Erblichkeitslehre (Jena: G. Fischer, 1909). 3. The Haidy-Weinberg equilibrium formula for Mendelian populations may be stated as follows: if in a large population pj is the proportion of gene Aj and p2 is the proportion of gene Aj, then after one generation of random mating the geno¬ types will attain and remain at the following frequencies: Genotype Frequency AjAj p] AjAj 2pjP2 A2A2 P2 The original papers are G. H. Hardy, Mendelian Proportions in a Mixed Population, Science, 28(1908):49-50;and W.Weinberg, Über den Nachweis der Vererbung beim Menschen, Jahreshefte Verein f. Vaterl. Naturk. in Württemberg, вЛ{\90%)\Ъв9-^2.
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