In chickens, black plumage dominates over red, the presence of a ridge over its absence.

In chickens, black plumage dominates over red, the presence of a ridge over its absence. The genes encoding these traits are located on different pairs of chromosomes. A red rooster with a comb is crossed with a black hen without a comb. Numerous offspring were obtained, half of which have black plumage and crest, and half have red plumage and crest. What are the most likely genotypes of the parents.

Let’s designate the gene that determines the black color of the plumage of chickens as A, then the gene for the red color of the feathers will be a.

Let’s designate the gene that determines the development of the ridge in chickens as C, then the gene that causes its absence in the homozygous state will be c.

Since all chickens have a comb, and from a hen without a comb (cc) they receive only the recessive gene c, it can be concluded that the rooster is homozygous for the gene for the presence of a comb.

Since half of the chickens have red plumage, and this trait develops only if it is homozygous in the genotype – aa, it should be concluded that the black chicken is heterozygous (Aa), the carrier of the gene for the recessive trait.

Let’s write down the most probable genotypes of a rooster and a chicken.

The chicken is black and has no crest – Aass, it produces Ac and ac oocytes.

The rooster is red and has a comb – aAC, produces aC sperm.

Chickens: black with a crest (AaCc) – 50% and red with a crest (aaCc) – 50%, which corresponds to the results of crossing from the problem statement.

Answer: Ааcc (chicken) and ccСС (rooster).