Two genes control fur color in Labrador retrievers. The first gene determines whether the pigment to be deposited in the hairs will be black or brown. The second gene determines whether the pigments are put into the dog's hairs at all. A dog homozygous for the recessive allele of this second gene will be yellow because no pigment is deposited in its hairs. This is an example of
A)epistasis.
B)pleiotrophy.
C)codominance.
D)incomplete dominance.

Question

Quizplus · Accepted Answer

This scenario is an example of epistasis because the expression of one gene (the second gene) is dependent on the presence of another gene (the first gene). If the first gene produces the dominant allele, then the second gene will be expressed and the dog will have black or brown fur. However, if the second gene is homozygous recessive, then the expression of the first gene does not matter - the dog will not have any pigment deposited in its hair and will be yellow.

Two Genes Control Fur Color in Labrador Retrievers