This is the notebook for chapter 5 in Genetics and Analysis of Quantitative Traits. Epistasis Epistasis describes the nonadditivity of effects between loci. Consider an individual with alleles (A_i) and (A_j) at one locus and (B_k) and (Bl) at another. [G{ijkl}=\mu_G+(\alpha_i+\alphaj+\delta{ij})+(\alpha_k+\alphal+\delta{kl})+\epsilon_{ijkl}] With only two loci, there are actually three ways in which interactions can arise between loci: (additive \times additive)((\alpha\alpha)), (additive \times dominance)((\alpha\delta)), (dominance \times dominance)((\delta\delta\ …