From The School of Biomedical Sciences Wiki
Jump to: navigation, search

Epistasis is an interaction in which the genotype at one locus will mask/suppress the phenotypic expression of the genotype at another locus[1].

An example of epistasis occurs in Labrador Retriever coat colour. Coat colour of Labrador Retrievers is determined by two genes: the B gene and the E gene and the phenotypes can be either black coats, chocolate brown coats or yellow coats. A dominant B and a dominant E gene present in the genotype (e.g. BBEE, BBEe, BbEE, BbEe) will give a Labrador with a black coat, a dominant E gene present with recessive B genes (e.g. bbEe, bbEE) will give Labradors with a chocolate brown coats. However, the genotype of recessive E (e) is recessive but also epistatic in homozygous form (ee) so if the genotype 'ee' is present the Labrador will have a yellow coat, regardless of the B gene genotype. This is an example of epistasis as the genotype at the E gene determines the expression of the B gene[2].


  1. Daniel L. Hartl, Maryellen Ruvolo, (2012) Genetic:s analysis of genes and genomes, 8th edition, Burlington, Massachusetts: Jones and Bartlett Learning
  2. https://online.science.psu.edu/biol011_sandbox_7239/node/7371
Personal tools