What is the term for gene-to-gene interaction in which the action of one gene modifies the expression of a different gene?

The term that describes the gene-to-gene interaction where the action of one gene modifies the expression of another gene is epistasis. In genetic studies, epistasis plays a crucial role in understanding how different genes interact and how these interactions can affect phenotypes. This concept indicates that one gene can mask or alter the phenotypic expression of another gene, which can complicate the inheritance patterns expected from Mendelian genetics.

For instance, in a classic example involving coat color in mice, one gene may determine the pigment type, while another gene might influence whether the pigment is actually deposited in the hair. If the second gene is not functional (epistatic), it can prevent the expression of the first gene, regardless of its allele configuration. This illustrates how epistasis can significantly complicate the relationships between genotypes and phenotypes in various organisms.

The other terms do not capture this specific interaction:

• Allele modification generally refers to changes in alleles and does not encompass the interaction between different genes.

• Gene regulation refers to the processes that control the expression of a gene, which can involve multiple mechanisms but does not specifically imply interaction with a different gene.

• Mutation impact typically addresses how changes in a single gene can affect an organism, rather