A test for linkage of the loci for dominant white and barring with loci controlling growth rate in the fowl1

Publisher Website
Google Scholar
Abstract
Females from a coloured inbred line of Leghorns (ii) were mated to three groups of males heterozygous for the dominant white gene (Ii). The parents transmitting the I gene to the three groups of males were respectively larger, smaller and of the same size as the parents transmitting the i gene. No differences were observed between the three types of crosses in the effect of colour genotype on body weight, providing no evidence for linkage between the dominant white locus and loci affecting body weight. When comparisons were made between the colour genotype classes, pooled within full sib groups, the coloured genotype was larger in ten of the twelve test cross‐sex‐hatch combinations. Two of these differences, were statistically significant, but when the data were pooled over hatch, sex and test cross, no significant difference was found. The data thus offer meagre support for weight differences in favour of the coloured genotype, but the negative evidence of the pooled analysis raises considerable doubt that real differences in weights between the colour classes exist in these populations. A similar comparison was made between the barred and non‐barred genotypes among the coloured female progeny in one test cross. The barred progeny were heavier in each hatch, in spite of the fact that the barring gene and sex chromosome were derived from the smaller grandparent. The differences were not statistically significant in either hatch or when the mean squares were pooled over hatches. It is concluded, therefore, that this experiment provides no evidence for any association between the barring locus and the genes for growth rate in this population.