Review

1. 9A_B_:3aaB_:3A_bb:1aabb   (3/4)A_+1/4aa) (3/4B_+1/4bb)
   Due to two loci segregating for two different traits which are not linked with dominance gene action at each loci.
   
   
2. 9 purple:7white ratio is due to complementary epistasis with dominance gene action at each locus and genes at two unlinked loci interacting to influence a single trait.
   
   
3. 15 purple:1 white ratio is due to duplicate epistasis with dominance gene action at each locus and genes at two unlinked loci interacting to influence a single trait.
   
   
4. (1/2A+1/2a)² = 1/4 AA + 1/4Aa + 1/4aA + 1/4aa
                      = 1/4 AA + 1/2 Aa + 1/4aa
   This is an array of zygotes formed by gametes uniting.  We are expanding a gametic array to derive the proportions of zygotes.
   
   
5. (1/2Aa + 1/2aa)²= 1/4 (two Aa)
                           +1/2(one Aa and one aa)
                           + 1/4 (two aa)
   This is an array of families with two offspring formed by expanding a zygotic array to derive the proportions of each type of family.