Letter | Published:

Change of Linkage in Poultry with Age

Naturevolume 115page641 (1925) | Download Citation



Two dominant sex-linked Mendelian factors in the domestic fowl are known from the work of W. E. Agar (Journ. Genet., vol. 14, pp. 265–272, 1924), J. B. S. Haldane (Sci., vol. 54, p. 663, 1921), and G. S. Serebrovsky (Amer. Nat., vol. 56, p. 571–572, 1922), to exhibit partial linkage during spermatogenesis, as was to be expected if both are carried by the same chromosome. One of these, B, causes barring of the feathers; the other, S, causes silver as opposed to gold hackles. We have synthesised five cocks of composition, BS bs, i.e., receiving both these factors from one parent only, and mated them with bs hens. Thus each of the four possible types of spermatozoon gave rise to a different type of chick. So far 648 chicks have been counted. We find that the linkage between B and S becomes progressively weaker with the age of the cocks. In their first, second, and third breeding years respectively these have given 22.9 ± 1.4 per cent., 36.9 ± 2.9 per cent., and 47.6 ± 3.6 per cent, of cross-overs. Thus by the third year linkage has practically disappeared.

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