Table 4

An example of an interaction between the maternal and zygotic genotypes. (The locus expressed in offspring has two alleles, A1 and A2, with frequencies p1 and p2 while the maternal genotype is defined by a second locus that has two alleles, B1 and B2, with frequencies x1 and x2. The cells show the expected offspring (zygotic) phenotypes and the frequencies (in parentheses) of the nine maternal–offspring genotype combinations. The locus shows an additive-by-additive interaction effect, where the additive maternal effect depends on the offspring genotype and vice versa. The A1 allele has a+a effect on the offspring phenotype while the A2 allele has a−a effect. The column labelled gives the mean phenotypes of offspring produced by the three maternal genotypes at the B locus while gives the mean phenotypes of the three offspring genotypes at the A locus.)

offspring genotype

A1A1A2A1A2A2
maternal genotypeB1B1+a ()0 ()a ()+a(p1p2)
B1B20 ()0 ()0 ()0
B2B2a ()0 ()+a ()a(p1p2)
+a(x1x2)0a(x1x2)