In chickens, comb shape is determined by two interacting genes (R/r and P/p). A

Question

In chickens, comb shape is determined by two interacting genes (R/r and P/p). A walnut comb is produced when at least one dominant R allele and at least one dominant P allele are present (R- P-). A rose comb is produced when at least one dominant R allele is present and the second gene is homozygous recessive (R- pp). A pea comb is produced when the first gene is homozygous recessive and at least one dominant R allele is present (rr P-). When both genes are homozygous recessive, a single comb is produced. Predict the phenotype ratios for each of the following matings: Rr Pp X rr pp Rr pp X rr Pp

Explanation / Answer

1) Rr Pp X rr pp

Answer: 1/4 walnut (Rr Pp),

             1/4 rose (Rr pp),

             1/4 pea (rr Pp),

             1/4 single (rr pp)

2)    Rr pp X rr Pp

    Answer: 1/4 walnut (Rr Pp),

                  1/4 rose (Rr pp),

                  1/4 pea (rr Pp),

                  1/4 single (rr pp)

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