How does epistasis affect phenotypic expression?

Epistasis refers to the interaction between genes, where the effect of one gene is modified by one or several other genes. This can significantly influence the expression of phenotypes. In cases of epistasis, the presence of a particular allele at one gene can mask or change the effects of alleles at another gene. This interaction means that the phenotypic expression is not determined solely by one gene but is influenced by the interplay of multiple genes.

For example, if one gene controls the color of fur in an animal while another gene influences a modifier trait, the epistatic interaction might result in a completely different fur color than would have been expected from either gene acting independently. Thus, understanding epistasis is crucial in predicting phenotypic outcomes since it shows how genes can interrelate to produce a variety of observable trails, rather than acting in isolation. This highlights the complexity of genetic expression and the importance of genetic background in determining phenotypes.