. Animal biology. Biology; Zoology; Physiology. INHERITANCE 303 Furthermore, in considering dihybrids we found, for instance, that genes for yellow and round, and green and wrinkled seeds were inherited in a fashion which indicated that yellow and round are segregated independently of each other — there is an inde- pendent assortment because all possible combinations with green and wrinkled occur. This clearly is fully accounted for, provided the gene for color and the gene for form are not in the same pair of Gamete Gamete. Fig. 189. — Diagram to show the union of haploid groups of either the
. Animal biology. Biology; Zoology; Physiology. INHERITANCE 303 Furthermore, in considering dihybrids we found, for instance, that genes for yellow and round, and green and wrinkled seeds were inherited in a fashion which indicated that yellow and round are segregated independently of each other — there is an inde- pendent assortment because all possible combinations with green and wrinkled occur. This clearly is fully accounted for, provided the gene for color and the gene for form are not in the same pair of Gamete Gamete. Fig. 189. — Diagram to show the union of haploid groups of either the chromosomes or of the genes of the gametes to form the diploid condition of the zygote, body cells, and primordial germ cells. Finally their pairing at synapsis, and segregation in the gametes. With four pairs of chromosomes or of genes (Aa, Bb, Cc, Dd) there are sixteen possible types of gametes. chromosomes. Moreover, following synapsis the gametes secure one of each pair of homologous chromosomes (a haploid group), but not necessarily — indeed very rarely — all of maternal or paternal origin. (Figs. 183A, 189.) In short, when two gametes unite, each contributes to the zygote a homologous haploid group of genes with the result that the off- spring is of diploid gene constitution. Similarly, each gamete contributes a homologous haploid chromosome group so that the zygote is of diploid chromosome constitution. Thus both the chromosomes and the genes (characters) are in the haploid condi-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Woodruff, Lorande Loss, 1879-1947. New York The Macmillan company
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