In a cow, black color (A) dominates over red, and Hornlessness (B) – over horniness.

In a cow, black color (A) dominates over red, and Hornlessness (B) – over horniness. They crossed a black hornless bull and a red horned cow and got a red horned calf.

According to the notation introduced in the condition of the problem, we write down the genotype of the born calf: aabb, because homozygosity is a necessary condition for the realization of both traits that it possesses.

To be the parents of such a calf, both the bull and the cow must carry genes for recessive traits in their genotypes. If outwardly the parent individuals demonstrate manifestations of dominant genes, then they are necessarily heterozygous.

The cow is red and horned – aabb, like the calves. Her body produces eggs ab.

The bull is black and has no horns – AaBb, the spermatozoa it produces are AB, ab, aB and Ab.

All possible offspring of the given cow and bull will look like this:

25% AaBb, which corresponds to hornless calves with a black coat;

25% aabb – horned red calves;

25% aaBb – corresponds to red hornless calves;

25% Aabb – corresponds to black calves with horns.