Problem Set 3 -Answers 1. Because 1/64 is the ratio expected for the homozygous recessive phenotype in the F2 generation of a trihybrid cross. 2. No, because an additive allelic series involves more than one gene. The alternative alleles at those loci are added together to produce the final phenotype. 3. 2/12 black manx female 2/12 tortoiseshell manx female 1/12 black normal female 1/12 tortoiseshell normal female 2/12 black manx male 2/12 orange manx male 1/12 black normal male 1/12 orange normal male