Sex-Linked Reduction of Body Size in Golden Sebright Bantams

Abstract

Sires heterozygous for Z sex chromosome replicates from two Golden Sebright Bantam cocks and one broiler-type male were mated to Leghorn and 1/4 Sebright dams. The sex chromosome of the broiler-type male was marked by the genes K and Id. The sex chromosomes of the Sebright Bantams were marked by the k and id genes.The K daughters of the Leghorn dams were statistically heavier than their k sisters (P<0.01) at 8 and 16 weeks of age, while the K daughters of the 1/4 Sebright dams were heavier than their k sisters (P<0.05) only at 24 weeks of age. Mature shank lengths of K daughters from both kinds of dams were significantly longer (P<0.01) than those of their k sisters. The weights and shank lengths of Id daughters of the Leghorn dams were similar to those of their id sisters.The differences between the 8-week body weights of slow and rapid feathering brothers were statistically significant for the sons of the Leghorn dams (P<0.01) and for the sons of the 1/4 Sebright dams (P<0.05). Sex dimorphism for body weight at 8 weeks of age was higher among the rapid feathering progeny of the Leghorn dams, the males being 36% heavier than their sisters.The data presented give additional evidence that a recessive sex-linked gene near the K locus is responsible for part of the small body size in the Sebright Bantams. It is suggested that this “bantam gene” is possibly an allele of the dw gene and the symbols dw+ an d dwB are proposed for the normal and bantam alleles.