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910
In eugenics1, attention is directed primarily to the role of heredity2, the transmission of human characteristics from generation to generation, operating through genes3, which are transmitted to children by their parents. The development of eugenic theory is dependent on the progress of genetics4 (cf. 103-4*), the science concerned with the transmission and effects of hereditary factors. Eugenics as a social movement refers to policies aimed at improving the quality of human populations.
- 1. eugenics n. — eugenic adj. — eugenist n., a specialist in eugenics. 4. genetics n. — genetic adj. — geneticist n., a specialist in genetics.
911
A distinction has sometimes been attempted between hereditary characteristics1, which are inherited, and acquired characteristics2 which are not so transmitted. This is now viewed as a distinction of degree only, because most phenotypic3 characteristics, i. e., observed characteristics, involve the interaction of both genotypic4, i. e., inherited factors, and environmental factors. The characteristics determined by a dominant5 gene (901-3) will appear in all who inherit it; this is not true of a recessive6 gene. The dominance of a gene, however, may be incomplete or its influence may be masked by other geaes in polygenic action. A lethal characteristic7 generally brings about the early death of the foetus (602-7). Changes in genes, called mutations8, are chance variations, and may be pathological in effect. Panmixia9 is the formation of unions (501-3) at random, i. e., without regard to the affiliation of the parties to genetic groups.
912
A distinction is often made in eugenic policy between positive eugenics1 aimed at increasing the number of persons believed to have desirable characteristics, and negative eugenics2 aimed at restricting the reproduction of persons expected to transmit undesirable characteristics or hereditary defects3. Much attention has been given to the discussion of eugenic sterilization4, i. e., the sterilization of persons likely to transmit undesirable characteristics to their descendants. Objections to this measure have been raised on moral grounds and also because of its relatively low efficiency in reducing the frequency of recessive genes (911-6). Among the measures proposed, pre-marital examination5 may be mentioned; this is designed to give couples intending to marry information about the probable quality of their offspring, so that prospective partners to dysgenic marriages6, i. e., those likely to produce defectives, may be warned.
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