Genetics of Chicken Combs

The combs of chickens are controlled by four alleles, which interact to produce four distinct phenotypes: single, rose, pea, and walnut.

This exercise asks students to predict the outcomes of chicken crosses. Ideally, students should already know how to do crosses that involve two traits, the mechanisms for solving these problems are similar.

My honors biology (AP Biology) students are encouraged to use mathematically probability to solve crosses that involve multiple traits. 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.

Male chicken with single comb.

For more information on the genetics of chicken combs:

Primary Literature: The Rose-comb Mutation in Chickens Constitutes a Structural Rearrangement Causing Both Altered Comb Morphology and Defective Sperm Motility

9 Comb Types, Backyard Chicken

Poultry Genetics for Small and Backyard Flocks

Grade Level:  9-12
Time Required:  15-20 minutes

Download PDF Google Doc Key (TpT)

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