What term describes the interaction between two or more genes to control a single phenotype?

The term that describes the interaction between two or more genes to control a single phenotype is epistasis. In epistasis, the expression of one gene can mask or alter the expression of another gene at a different locus. This means that the presence of certain alleles can influence the outcome of another gene's alleles, effectively determining the phenotype observed.

For example, in some cases, one gene may determine a particular trait (like color), while another gene may modify the expression of that trait. This complex interaction is crucial in genetics because it illustrates that phenotypes are not merely the result of single genes acting independently, but rather through intricate networks of gene interactions. Understanding epistasis is vital for deciphering how traits are inherited and expressed in organisms.

Other options describe different genetic principles but do not directly relate to the interaction of multiple genes controlling a single phenotype. Dominance refers specifically to relationships between alleles of the same gene, polygenic inheritance involves multiple genes contributing to a single phenotype without necessarily interacting with each other, and codominance describes a situation where both alleles in a heterozygote contribute to the phenotype independently, rather than one masking the other.