. Animal biology. Biology; Zoology; Physiology. ,. A^. y/^ssfy **&* r ? : ?. J- i •«<* 3-s£u- %;j^. Fig. 183B. — Result of crossing pure smooth black with rough white Guinea- pigs. Rough and black (pigmented) are dominant. Note that each parent (P) bears both a dominant and a recessive character. The F2 illustrates the principle of independent assortment. 3. Trihybrids Similarly, Mendelian trihybrids, for example the cross between pure tall Peas bearing yellow round seeds and dwarfs bearing green wrinkled seeds, or the cross between pure Guinea-pigs with long, rough, black hair and thos
. Animal biology. Biology; Zoology; Physiology. ,. A^. y/^ssfy **&* r ? : ?. J- i •«<* 3-s£u- %;j^. Fig. 183B. — Result of crossing pure smooth black with rough white Guinea- pigs. Rough and black (pigmented) are dominant. Note that each parent (P) bears both a dominant and a recessive character. The F2 illustrates the principle of independent assortment. 3. Trihybrids Similarly, Mendelian trihybrids, for example the cross between pure tall Peas bearing yellow round seeds and dwarfs bearing green wrinkled seeds, or the cross between pure Guinea-pigs with long, rough, black hair and those with short, smooth, white hair give in the F2 generation 27 genotypes and 8 phenotypes; the number of individuals in the phenotypes being in the ratio 27 :9 :9 :9 : 3:3:3:1. Of course, in nature there are few instances in which parents and offspring differ by only one, two, or three characters, but since characters arising from each pair of allelomorphs can usually be treated singly, convenience demands that the analysis be made with respect to one or two pairs at a time, which there- fore is the usual method of procedure. (Figs. 184, 185.) 4. Summary Before passing to certain extensions of these established hered- itary principles, it may serve to clarify the subject if we restate. 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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