Question

Four comb types are commonly seen in chickens (Gallus gallus domesticus): Walnut, Rose, Pea and Single (see figure). Comb phenotype is controlled by two genes, R and P. When at least one dominant allele of the R gene is present and the P gene is homozygous recessive, a Rose comb will arise; when at least one dominant allele of the P gene is present and the R gene is homozygous recessive, a Pea comb will arise. When at least one dominant allele of both genes is present, a Walnut comb will arise. If both genes are homozygous recessive, a Single comb will arise. A. (5 points) If a true breeding Walnut comb cock is bred with a Single comb hen, what will be the comb phenotype(s) with corresponding proportions of the F1 offspring? B. (5 points) If two F1 chickens are bred together, what proportion of the offspring will display a Pea comb? C. (5 points) List and briefly explain two ways of getting the answer for B.

Answer 1