What does epistasis refer to in genetics?

Epistasis in genetics refers to the phenomenon where the expression of one gene influences or masks the expression of another gene. This interaction can occur when two or more genes contribute to a single phenotype, and one gene can thereby modify or completely alter the effect of another. For example, in the case of coat color in certain animals, one gene may determine the presence of pigment, while another gene determines the type of pigment produced. If the first gene is not expressed due to its epistatic interaction with the second gene, the overall phenotype will reflect this influence.

Understanding epistasis is crucial for studying genetic interactions and predicting phenotypic outcomes, as it highlights that the relationship between genes is often more complex than a simple additive model. This concept helps clarify why certain traits do not always follow Mendelian inheritance patterns and can instead display more intricate genetic behaviors. The other options, while related to genetics in general, do not specifically define the intricate interactions represented by epistasis.