Two Genes Control Fur Color in Labrador Retrievers

Multiple Choice

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.