A Quantitative Study of Variations in Intensity of Genotypes of the Guinea Pig at Birth.

Genes F , f make no difference in dark sepias (1) or dark browns ( 3 ) (with a minor qualification in the latter). No difference between B and b b has been detected in the pale brownish creams ( 5 ) . Neither of the pairs B, b or P , p make any difference in coat colors of yellows (6,7) at birth but do make a difference in the sootiness that often develops later in yellows. They also make a difference in the color of the skin especially in the ears, feet and nose which are dusky to black with BP, brown with bbP and very pale with pp. Skin color is similar in quality in yellows and nonyellows but less intense in the former. Eye color in yellows depends on B,b, P,p in the same ways as in nonyellows, (CBP Dark, CbbP brown, C-pp pink). Any of the eumelanic colors (1 to 5 ) may be combined with the corresponding yellow in a tortoise-shell pattern by substitution of e* for E . These same colors may be combined in a banded pattern in each hair (agouti) by substituting A for aa. This substitution has no effect on yellows at birth, but the presence of A is revealed in adult sooty yellows by a clear yellow subterminal band, like that in agoutis. Much of the data of the present paper is derived from tortoise-shells but none from agoutis. The variations in intensity of these seven series depend primarily on the combinations of the C alleles (C, ck, 6, c7, p ) that are present. C (dominant) determines the highest intensity (with qualifications in the case of the dark brown). With c a p there is albinism, white with pink eyes, irrespective of anything else. E a a B P E aa B pp F E a a b b P E aa b b p p F E aa p p ff