. Analysis of development. Embryology; Embryology. 154 The Nucleus and Cytoplasm in Development of alleles such as those responsible for the human iso-agglutinogens A and B and the antigens themselves, as shown by the facts that whenever the relevant allele is present the antigen appears in every genetic back- ground, and that in heterozygotes for the alleles I* and F both antigens A and B are produced simultaneously. It has also been assumed that enzymes, which control a variety of biochemical re- different rates of gene-controlled, qualita- tively identical reactions and has shown how such a
. Analysis of development. Embryology; Embryology. 154 The Nucleus and Cytoplasm in Development of alleles such as those responsible for the human iso-agglutinogens A and B and the antigens themselves, as shown by the facts that whenever the relevant allele is present the antigen appears in every genetic back- ground, and that in heterozygotes for the alleles I* and F both antigens A and B are produced simultaneously. It has also been assumed that enzymes, which control a variety of biochemical re- different rates of gene-controlled, qualita- tively identical reactions and has shown how such a rate concept fits a great variety of phenomena in developmental genetics. In some cases, different rates of production of pigments or of growth, controlled by differ- ent alleles, have been demonstrated by direct observation (Fig. and B). These different rates have been reported by Goldschmidt ('27) for larval pigmentation in Lymantria /^ ^^^'-''""" ('' /// v .^ Instors Ez:. Sexual maturity Sexual maturity of normal males of dwarf males begins begins 80 30 40 50 Time in days Fig. 38. A, Pigmentation curves of seven different geographic races of the gypsy-moth Lymantria dispar (after Goldschmidt, '27). B, Growth curves for a normal (GG) and a "dwarf" {gg) strain of Gammarus chevreuxi (after Ford and Huxley, '29). actions in the bread mold Neurospora, are under immediate gene control in the sense that specific alleles impress enzymatic spec- ificity on cellular constituents (Beadle, '45; Bonner, '48; Horowitz, '50). Attempts to prove this hypothesis have met with great difficulties (Emerson, '50). The examples of gene-controlled antigens and enzymes indicate that the primary prod- ucts of the action of different alleles may be qualitatively different. There are other examples which suggest quantitative differ- ence in allelic action. A series of multiple alleles of a given gene visually affects the same phenotypic trait, in a graded manner. In Droso
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