. Biology. Biology. MENDELIAN INHERITANCE 223 may unite with a yellow-bearing ovule, and the result is a heterozygous yellow, since yellow is dominant. Or a yellow- bearing anther may unite with a yellow-bearing ovule, giving a homozygous yellow; or finally a yellow-bearing anther may unite with a green-bearing ovule, giving a heterozygous yellow. Thus there will be three yellows to one green or one pure yellow, two heterozygous yellows and one pure green (Fig. 94, F2 generation). Mendel found further, that these pure greens, if continually self-fertilized, never gave rise to yellow peas, and
. Biology. Biology. MENDELIAN INHERITANCE 223 may unite with a yellow-bearing ovule, and the result is a heterozygous yellow, since yellow is dominant. Or a yellow- bearing anther may unite with a yellow-bearing ovule, giving a homozygous yellow; or finally a yellow-bearing anther may unite with a green-bearing ovule, giving a heterozygous yellow. Thus there will be three yellows to one green or one pure yellow, two heterozygous yellows and one pure green (Fig. 94, F2 generation). Mendel found further, that these pure greens, if continually self-fertilized, never gave rise to yellow peas, and that the pure PARENTS. FIG. 96.—Diagram to illustrate the history of the gametes of crossed white and red Mirabilis. A gamete with factor for white and one with factor for red unite to form the pink zygote of FI. The gametes in FI are homozygous for red or white, and these, by random mating, give the Mendelian ratio. (From Morgan.) yellows never gave rise to green peas, while the mixed yellows and greens, on self-fertilization, always produced offspring in the proportion of three yellow to one green. A similar result is obtained with white and red races of Mirabilis jalapa, the "four o'clock," in which the hybrid (F), is pink (Figs. 95 and 96). Here both allelomorphs for color take part in the hybrid flower, forming a composite pink (Fi) which,. 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 Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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