5. In chickens, the dominant allele of one gene (R) determines a rose comb shape

Question

5. In chickens, the dominant allele of one gene (R) determines a rose comb shape and the dominant allele of a different gene (P) determines pea comb shape. If at least one dominant allele of both genes is present, a walnut comb shape is observed. The recessive alleles of each gene, when present together in a homozygous state, give a "single comb" shape. Rose-combed chickens are mated with walnut combed chickens and the following progeny are observed 15 walnut-combed chickens 14 rose-combed chickens 5 pea-combed chickens 6 single-combed chickens The genotypes of the birds used in this cross was: A. RRpp X RrPp B. RrPp X RrPp C. Rrpp X RrPp D. Rrpp X RRPP E. RRPP X Irpp

Explanation / Answer

In chickens, the gene R determines the presence of rose comb shape and the gene P determines the presence of pea comb shape. If one dominant allele of both genes are present, walnut comb shape is obtained. The recessive alleles in homozygous state produce single comb shape.

Rose combed chickens are mated with walnut combed chicken. The mating between Rrpp and RrPp is given in the following punnett square,

The walnut combed, rose combed, pea combed and white combed chicken are produced in the ratio of 3:3:1:1 which corresponds to the results obtained.

So, the answer for this question is option C.

Rp Rp rp rp RP RRPp RRPp RrPp RrPp Rp RRpp RRpp Rrpp Rrpp rP RrPp RrPp rrPp rrPp rp Rrpp Rrpp rrpp rrpp

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