Genetics of Chicken Combs
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Multiple Allele Traits in Chickens - The combs of chickens are controlled by four alleles, which interact to produce four distinct phenotypes: single, rose, pea, and walnut. The comb is a fleshy growth on the top of the chicken's head. Both male and female chickens have combs, but the ones on the male are larger. There are four varieties of combs:
Punnet squares become unwieldy when multiple alleles are involved. Many of the questions can be solved visually, without using math or a Punnet square. For example the cross rrpp x RRPP will always produce chickens with the genotype RrPp, which will have walnut combs.
For each cross, indicate the expected phenotypes.
1. Rose comb (RrPp) and Pea Comb (rrPP)
Single _____
Rose ____
Pea ____
Walnut ____
2. Single comb x Walnut (RrPp)
Single _____
Rose ____
Pea ____
Walnut ____
3. Single comb x Pea comb (rrPp)
Single _____
Rose ____
Pea ____
Walnut ____
4. Single comb x Pea comb (rrPP)
Single _____
Rose ____
Pea ____
Walnut ____
5. Walnut combs (both heterozygotes) RrPp x RrPp
Single _____
Rose ____
Pea ____
Walnut ____