Question

An incompletely dominant gene controls the color of chickens so that BB produces black, Bb produces a slate-gray color called blue, and bb produces splashed white. A second gene controls comb shape, with the dominant gene R producing a rose comb and r producing a single comb. If a pure-breeding black chicken with a rose comb is mated to a splashed white chicken with a single comb in the F2 generation, what fraction of the offspring will be blue with rose comb?

Answer 1

The fraction of the offspring that will be blue with a rose comb is 1/4 or 25%.

Step-by-step explanation:

In this case, the black chicken with a rose comb is homozygous for the coat color gene (BB) and dominant for the comb shape gene (RR). The splashed white chicken with a single comb is homozygous for the coat color gene (bb) and recessive for the comb shape gene (rr). When these two chickens are mated in the F2 generation, their offspring will inherit one gene for coat color and one gene for comb shape from each parent.

The possible genotypes of the offspring will be: BR, Bb, rR, and rr. However, only the genotype BbRr will result in a blue color with a rose comb. This means that 1 out of the 4 possible genotypes will produce the desired phenotype.

Therefore, the fraction of the offspring that will be blue with a rose comb is 1/4 or 25%.