In domestic cats, males are XYXYXY and females are XXXXXX. A gene on the XXX chromosome controls fur colour. The allele RRR codes for red fur and the allele DDD codes for dark fur. These alleles are codominant. Heterozygous females have red and dark patches of fur and their phenotype is described as tortoiseshell female. The two alleles, WWW and www of a different gene, which is not sex-linked, interact with the gene controlling fur colour. The allele WWW is dominant and stops the formation of pigment in the fur, resulting in white fur. The allele www is recessive and has no effect on fur colour.
Name the type of interaction between the two genes affecting fur colour.
What phenotype would a cat with the genotype XRXDwwX^R X^D wwXRXDww have?
Complete a genetic diagram to show all the possible genotypes and the ratio of phenotypes expected in the offspring of the cross:
XDXDWw×XRYww X^D X^D Ww \times X^R Y ww XDXDWw×XRYwwIn a population of these cats, 51%51\%51% of cats had the WWW allele and had white fur. Use the Hardy–Weinberg equation to calculate the frequency of the www allele in this population. Show your working.
