How is "epistasis" defined in genetics?

Epistasis is defined as a genetic phenomenon where the expression of one gene is modified or silenced by one or more other genes. This interaction between genes can result in one gene overriding or masking the effects of another gene, consequently influencing the phenotype of an organism.

In the context of Mendelian genetics, understanding epistasis is crucial as it illustrates how traits do not always independently segregate. By studying epistasis, researchers can discern the complexities of inheritance patterns and how certain phenotypes may arise due to the interactions of multiple genes rather than through the action of single pairs of alleles. This concept is fundamental when exploring genetic traits in various organisms and can lead to a more nuanced understanding of inheritance beyond simple dominance relationships.