. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 164 GENETICS IN RELATION TO AGRICULTURE be interested in tracing out others. Thus the presence of a factor for dominant white may be demonstrated by crossing with a purple race, in which case the grains will be white, if such a factor be present. More- over, several of the whites when crossed give colored forms in Fi, thus 11 X 13, 11 X 14, and 12 X 13 give purple, and 12 X 14 gives red. It has already been shown how in case of the presence of the factor for dominant white, whites when crossed may
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 164 GENETICS IN RELATION TO AGRICULTURE be interested in tracing out others. Thus the presence of a factor for dominant white may be demonstrated by crossing with a purple race, in which case the grains will be white, if such a factor be present. More- over, several of the whites when crossed give colored forms in Fi, thus 11 X 13, 11 X 14, and 12 X 13 give purple, and 12 X 14 gives red. It has already been shown how in case of the presence of the factor for dominant white, whites when crossed may give a white Fi and white, purple, and red in various proportions in i^2. Such is the case for ex-. FiG. 75.—ComI:) types in poiiLtry. Single, o; pea. h; rose, c; walnut, d; and breda, e. {After Mor{jan.) ample in the cross 1X16 which will give Fi white and F-, in the ratio 220 white:27 purple:9 red. The complex relations here existing between only three phenotypes is a very good example of the sort of problems which must be solved by experimental genetics. Comb-characters in Fowls.—A variety of comb-characters are found in the domestic breeds of poultry and Bateson has made these the sub- ject of an extensive Mendelian investigation involving the rearing of over 12,000 individuals. The comb types involved arc shown in Fig. 75. In this series of characters both rose and pea comb were found to be dominant to single comb, and give in F^ simple 3:1 ratios. These relations obviously indicate that there is a single factor difference be- Digitized by Microsoft®. 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 Babcock, E. B. (Ernest Brown), b. 1877; Clausen, Roy Elwood, 1891-. New York, McGraw-Hill; [etc. , etc. ]
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