Epistasis

Epistasis ( Greek for slow stop ) is a form of gene interaction. It is when a gene capable of effecting suppression of the phenotypic expression of any other gene. The term was introduced in 1909 by William Bateson. There are dominant and recessive epistasis. Controlled by a single gene multiple phenotypic traits, we speak of pleiotropy.

In the more general definition of the term epistasis is the interaction of genes between alleles at different loci. Thus, the epistasis is a phenomenon of non-additive genetic variance, so that genetic material are not simply a " mix" of the alleles of the parental generation. In other words, epistasis is before if and only if the effects of different loci are dependent on each other, the covariance of the contributions of zero is so different. Through this interaction effects there is an additional variation between parental and filial generation.

Example

Consideration of mice with three coat colors: Brown, Black, and White. Black is dominant over brown. There are three colors for the two genes: one can be in the form B (black) or b ( brown ) are present, the other in the form C ( colored) or c (not colored). The first gene depends on which pigment is produced from the second, if at all, a pigment is produced. The second gene is epistatic to the first. When crossing two mice with the genotype Bb C c is thus obtained to 4/16 white mice (cc (regardless of the pigment) ) to 3/16 brown mice ( bb and cc or CC) and 9/16 black mice ( Bb or BB, Cc or CC).