Epistatic dogs

Epistasis at work: The effect of two different gene alleles on coat color in dogs

Epistasis is the interaction between genes that results in modification of the phenotype of one of the genes. Epistasis can lead to the creation of a new phenotype or its suppression[1]. In some cases, the  term epistasis is used to describe traits that appear to interact statistically. However, statistical interpretation of interaction does not always imply biological interaction [2]. Epistasis also affects polygenic traits with quantifiable variation and is considered when studying quantitative traits that vary based on the genetic background on which they are expressed [3].

Quantitative Trait Loci (QTL)Edit

Quantitative traits are phenotypes that vary in presentation because they are the product of two or more genes i.e. they are polygenic traits. Quantitative traits like skin pigmentation or height usually exist as a continuum and can be measured [3]. In the study of epistasis, the loci at which genes involved in quantitative traits are found (quantitative trait loci (QTL)) are usually studied.  QTL can be studied to determine which genes are really influencing the expression of a gene/ protein of interest [4].  Genes in a QTL can be identified by methods such as transgenesis where the entire segment of DNA is inserted into a BAC and used to transfect a model organism zygote. In such cases the offspring produced can be screened for the quantitative phenotype to identify genes involved in its expression [4]. The function of genes in a QTL can also be studied to determine other genes at that locus that regulate its level of activity [5].


1. Miko, I. (2008) Epistasis: Gene interaction and phenotype effects. Nature Education 1(1)

2. Cordell H.J (2002) Epistasis: what it means, what it doesn't mean, and statistical methods to detect it in humansPMID:12351582

3. Carlborg O, Haley C.S (2004) Epistasis: too often neglected in complex trait studies?PMID: 15266344 (pdf)

4. Abiola O, Angel M.J et al. (2003) The nature and identification of quantitative trait loci: a community's view PMID: 14634638

5. Harjes CE, Rocheford TR et al. (2008) Natural Genetic Variation in Lycopene Epsilon Cyclase Tapped for Maize Biofortification  PMID: 18202289

6. PMID: 18202289