Linear Relationship of the Loci for Barring, Dermal Melanin Inhibitor, and Recessive White Skin on the Chicken Z Chromosome

The Z-linked loci barring (B), dermal melanin inhibitor (Id), and recessive white skin (y), and the MN t(Z;1) Z-linked chromosome translocation breakpoint (TB) were tested for linkage relationships. The linear order was found to be B-Id-TB-y, with B distal from the centromere on the long arm of the chromosome, and y mapping closest to the centromere. Calculated map unit values between markers varied depending on the presence or absence of the chromosome translocation. When tested on a normal chromosome, map distance +/- SE between B and Id was 13.7 +/- 2.2, and the Id-y distance was 39.9 +/- 3.0. The B and y loci showed independent segregation. When B and y were tested in the presence of the translocation, the calculated distance between these markers was 29.8 +/- 4.0. The B locus mapped 19.1 +/- 3.5 from TB, and y mapped 16.8 +/- 3.1 from TB.