Abstract
All of the numerous color modifications known in the domestic pigeon may be grouped under 3 basic types of pigmentation; black, chocolate, or red. Of these 3 types black and red are by far the best known. Their genetic relationships were fully studied by Cole. 1 Chocolate has long occurred in several varieties of pigeons but the breeder has commonly classed this color with dun (dilute black). It was first recognized as a distinct type of pigmentation by Metzelaar. 2 Three years later Christie and Wriedt 3 reported chocolate recessive and sex-linked in relation to black. The data here presented confirm their conclusion. The results of the chocolate × recessive red matings are also in general agreement with those just published by Metzelaar. 4 When the male parent is red and the female chocolate, blacks occur in both sexes in the F1. These results demonstrate an interaction between a factor for black carried by the red parent with an extension factor from the chocolate. In the reciprocal matings the results are modified by the sex-linked relations of the B factor. The data are presented in Table I, and an inspection of the results will show that the genetic relationships of the 3 basic color types in pigeons may be interpreted upon the basis of a 2 factor hypothesis. The factors are:
B—factor for black, b—chocolate, sex-linked.
E—factor for extension of black or chocolate, e—non-extension.
The linkage relations between chocolate and the intensity factor are being studied, and present results (2 crossovers: 7 non-crossovers) indicate a rather loose linkage between these factors. The pigment obtained by chemical extraction from chocolate feathers greatly resembles black in its general appearance but in solubility tests it seems more like red.
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