Epistasis is a condition in genetics, whereby the interaction of between genes influences the expression of a phenotype, in such a way that one gene represses or causes the expression of the other. Epistasis is an antagonistic interaction between genes. The presence of a particular gene affects the expression of the others.
An example of epistasis is the pigmentation in mice where the presence of two recessive alleles (aa) for coat color would always express itself in albino form regardless of the alleles of other genes present in the interaction.
Epistasis is the interaction of multiple genes that are not allelic in such a way that the mutation of a particular gene is dependent on the absence of mutation or the presence of mutation in either one or more genes which are referred to as modifier genes. Epistasis is an interaction at occurs at the phenotypic level.
In other words, epistasis is a situation in which the expression of one gene is influenced or affected by the expression of one or more other genes that are independently inherited.
The illustration above is an example of epistasis.
