What is epistasis?

Epistasis refers to a genetic phenomenon where the effect of one gene is suppressed or masked by another gene, meaning that one gene can influence or modify the expression of another gene's phenotype. This concept is essential for understanding complex traits and interactions between different genes in a genetic pathway.

When one gene has the ability to inhibit or alter the expression of another gene’s effect, it can lead to a variety of outcomes in terms of phenotype. This interaction can be crucial in processes such as the development of certain traits or the manifestation of diseases, where multiple genes interact in pathways.

While the other options touch on aspects of genetics, they do not capture the specific nature of epistasis. For instance, a trait affected by multiple genes refers to polygenic inheritance, which is not the same as the interaction described in epistasis. Interaction between alleles at different loci is a broader concept that does not specifically denote suppression but encompasses various forms of genetic interaction. Similarly, the dominance of one allele over another addresses a single-gene interaction rather than the multi-locus interactions characteristic of epistasis. Thus, the definition of epistasis as the suppression of one gene's phenotype by another is distinct and descriptive of this specific genetic interaction.