RESEARCH ARTICLE Open Access Body composition and ge i M

Full list of author information is available at the end of the articleWith respect to complex traits (i.e., phenotypes controlled by multiple genes), although people are still doubting the importance of epistasis or gene by gene interation [1], there is strong evidence that epistasis should not be neglected when studying complex traits [2-4]. For example, in mammals, coat color is controlled by interactions among several genes [5]. Furthermore, Brockmann et al. mately 33-36 % of the phenotypic variance observed in body weight and fat accumulation and 20-33 % of the vari-ance in muscle weight and hormone serum concentra-tions in mice. These results highlight the important role of epistasis in the control of phenotypic traits. In addition to the epistasis, imprinting effect is another important con-tribution to the phenotypic variance in complex traits. Cheverud et al. suggested that combing phenotype-based mapping and bioinformatics approaches could help t