A Sex-Linked Mutation Affecting Rate of Feathering in Chickens

A chick from normal feathering parents was classified as “late” feathering at hatching (pins of flight feathers shorter than their respective coverts). But, at 6 weeks of age, it was completely devoid of back feathers. This bird, a male, was used in breeding tests with mates of known rate of feathering genotypes. The results of these tests indicate that this very slow feathering trait was due to a mutation at the K locus on the sex-chromosome. The new allele is dominant to late (K) and to early (k). The term “slow” is suggested and the symbol KS. The probable order of dominance of the alleles at this locus is KN→KS→K→k. No interaction was noted between the K and T loci.