In cows, the black color of the coat (A) dominates over the red one (a). The stage is a bull with a black coat, and a cow

In cows, the black color of the coat (A) dominates over the red one (a). The stage is a bull with a black coat, and a cow is black and red. All calves in this stage are black. Determine the genotype of the bull.

All red-haired cows will have aa genotype, black cows will have A_ genotype (the second gene of a pair is unknown, since the presence of one dominant gene in a pair will in any case give a black color).

According to the condition, the bull and all the calves in the herd have a black coat color, that is, their genotype A_ necessarily contains one dominant gene.

Red cows produce gametes of two types: A and a. As a result of fertilization with the semen of a bull, zygotes of types A_ and _a are formed, where bull gametes are in place of the gaps. Since, according to the condition of the problem, no calves with red hair (aa) were found in the offspring of the herd, it can be concluded that the bull is capable of producing only gametes containing the dominant gene A. It has the AA genotype, that is, it is homozygous for the dominant trait.

Answer: the bull is homozygous for the dominant trait (AA).