Final answer:
Epistasis refers to the interaction where the expression of one gene masks or alters the expression of another gene at a different locus, not within the same locus. It can result in non-Mendelian inheritance patterns in traits such as the coat color of mice where certain alleles can be epistatic to others.
Step-by-step explanation:
No, epistasis does not involve interaction between alleles at a single genetic locus. Instead, epistasis is a phenomenon where the expression of one gene or set of genes alters or masks the expression of another gene at a different locus. Epistasis may occur in various patterns, including dominant, recessive, and duplicate epistatic interactions.
An example of epistasis can be observed in the coat color of mice. A particular gene (C) is necessary for pigment production. If a mouse has the recessive c allele, it will be albino, regardless of the alleles at another color locus A. This means that the genotypes AAcc, Aacc, and aacc all result in an albino mouse because the C gene is epistatic to the A gene.
Epistasis is important because it can explain why certain phenotypes do not follow the expected Mendelian ratios of inheritance. This complexity often occurs in gene pathways, where one gene's expression can be dependent on the function of another gene either preceding or following it in the biochemical pathway.