When a pair of genes is said to be in epistasis, the expression of one allele in one gene masks the expression of the other gene. There are two general types of epistasis: the dominant epistasis, and recessive epistasis.
You have identified two genes that control fur color in dogs. If dogs have a dominant allele "B", they will be black, otherwise, they will be brown. If dogs have a dominant allele "I", they will be white, otherwise, their phenotype will be determined by gene B. You cross two double heterozygous dogs (BbIi x BbIi) to produce puppies. 12 of the puppies have white fur color, 3 have black fur color, and 1 has brown fur color. This is an example of:
A. Genes in independent pathways
B. Recessive epistasis
C. Dominant epistasis
D. Synthetic lethal