Homozygous purelines in cattle can be obtained by : (1) mating of unrelated individuals of same breed. (2) mating of individuals of different breed. (3) mating of individuals of different species. (4) mating of related individuals of same breed.
The correct answer is (4)
Inbreeding increases homozygosity. So, mating of the related individuals of same breed will give homozygous purelines.
