TABLE 1

The relationships among the eight genetic parameters producing digenic segregation ratios in the F2 generation characteristic of classical epistasis (from Jana 1971)

Nature of epistasisRelationship among parametersaF2 ratio
ComplementaryA1 = A2 = D1 = D2 = AA12 = AD12 = AD21 = DD129:7
DuplicateA1 = A2 = D1 = D2 = −AA12 = −AD12 = −AD21 = −DD1215:1
DominantA1 = D1A2, A2 = D2 = −AA12 = −AD12 = −AD21 = −DD1212:3:1
RecessiveA1 = D1A2, A2 = D2 = AA12 = AD12 = AD21 = DD129:3:4
InhibitoryA1 = −A2 = D1 = −D2 = −AA12 = −AD12 = −AD21 = −DD1213:3
  • a Ai is the additive effect at locus 1; A2 is the additive effect at locus 2; D1 is the dominance effect at locus 1; D2 is the dominance effect at locus 2; AA12 is the interaction between A1 and A2; AD12 is the interaction between A1 and D2; AD21 is the interaction between A2 and D1; and DD12 is the interaction between D1 and D2.