What is the concept of epistasis?

The concept of epistasis refers to a genetic interaction in which the effects of one gene are modified or suppressed by another gene. This interaction can shape phenotypic outcomes in complex ways, as the expression of one gene may influence or overshadow the expression of another. For instance, in a scenario where two genes contribute to a particular trait, one gene may completely mask the phenotypic expression of the other, leading to unexpected results in an organism's appearance or behavior. Epistasis plays a critical role in the genetic architecture of various traits and diseases, as it helps to explain how genes can interact and how multiple gene pathways can contribute to a single phenotype.

In contrast, the other options describe different genetic phenomena. Reciprocal gene expression refers to a scenario where two genes may express complementary effects but doesn't capture the suppression aspect of epistasis. The competition between different alleles describes a scenario in which multiple variants of a gene influence a trait, but does not involve the modifying interaction characteristic of epistasis. A gene mutation refers to a permanent alteration of the DNA sequence that may affect gene function but is not about the interaction between two genes. Understanding epistasis is crucial for comprehending how complex traits are inherited and expressed in populations.