Final answer:
Epistasis is an antagonistic interaction between genes, where one gene masks or interferes with the expression of another. The alleles being masked or silenced are hypostatic to the epistatic alleles. The biochemical basis of epistasis is often a gene pathway.
Step-by-step explanation:
In epistasis, the interaction between genes is antagonistic, such that one gene masks or interferes with the expression of another. "Epistasis" is a word composed of Greek roots that mean "standing upon." The alleles that are being masked or silenced are said to be hypostatic to the epistatic alleles that are doing the masking. Often the biochemical basis of epistasis is a gene pathway in which the expression of one gene is dependent on the function of a gene that precedes or follows it in the pathway.