The gene for black suit in cattle dominates over the gene for red suit. A black purebred

The gene for black suit in cattle dominates over the gene for red suit. A black purebred bull was crossed with red cows. How many second generation calves out of 48 calves were red?

Let’s designate the gene responsible for the development of black wool as A, then the gene that determines the red suit will be a.

According to the condition of the problem, the bull is purebred, which means that among his descendants there were no owners of red wool. Its genotype is AA. It produces sperm A.

Cows with red color are homozygous – aa. The eggs they produce – a.

All the first generation of bulls and cows are Aa, they have a black coat and produce gametes A and a.

Second generation purebred black bull and red cows:

Black individuals (AA – 25% and Aa – 50%);

Individuals with red hair (aa) – 25%.

Imagine that 48 calves are all possible offspring of the second generation, then 25% of this number is 12 calves.

Answer: 12.