Question

A rooster with gray feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are gray, 6 are black, and 8 are white. What is the simplest explanation for the inheritance of these colors in chickens? What offspring would you predict from the mating of a gray rooster and a black hen?

Answer 1

Answer:

Alleles for feather colour exhibit incomplete dominance or co-dominance.

50% gray offspring + 50% black offspring

Explanation:

It means that the alleles for feather colour in the hen exhibit incomplete dominance or co-dominance over one another.

Assuming the allele for white colour is B, white colour will be b while the heterozygote Bb gives the gray phenotype.

Gray rooster + gray hen = 15 gray chicks, 6 black chicks and 8 white chicks.

15:6:8 is roughly 2:1:1 which is phenotypic ratio obtainable from crossing two heterozygous individuals as pointed out by Mendel.

Bb   x   Bb = 1BB, 2Bb, and 1bb

Crossing the gray rooster (Bb) with a black hen (bb):

Bb   x   bb = Bb, Bb, bb, and bb

          = 2Bb (gray):2bb (black)

50% of the offspring will be gray while the remaining 50% will be black.