ABSTRACT
Quantitative trait locus (QTL) mapping experiments using DNA markers yield controversial results concerning the importance of epistasis affecting complex traits. Using a unique experimental design and statistical tests, C. C. Cockerham and Z. B. Zeng were able to detect strong epistasis among linked loci which may behave as single ‘overdominant’ QTLs affecting many quantitative traits in maize. The concept to detect and quantify epistasis affecting complex traits using linked DNA markers is much the same as that in QTL mapping described in the previous sections. Although the quantitative genetic models for epistasis are complicated, the statistical models for detecting epistasis are straightforword. Epistasis is an important genetic basis for complex traits. Several lines of evidence in QTL mapping studies indicate that epistasis is commonly detected between QTLs and background loci, and between complementary loci which do not appear to have significant main effects.
