Pigmented eyes (P) are dominant to non-pigmented (p), and dimpled chins (D) are dominant to Non-dimpled chins (d). A pigment-eyed, dimple-chinned man marries a blue-eyed woman without a dimpled chin. Their firstborn child is blue-eyed and has a dimpled chin. What are the possible genotypes of the father

PpDD and PpDd

Explanation:

Pigmented eyes (P) are dominant to non-pigmented (p), and dimpled chins (D) are dominant to Non-dimpled chins (d).

The possible genotypes of a pigment-eyed, dimple-chinned person would be  PPDD, PpDd, PPDd, PpDD while a blue-eyed person without a dimpled chin would have the genotype ppdd.

The genotype of a blue-eyed, dimpled chin child would be either of ppDd or ppDD, but in this case, the mother is ppdd and as such, the child cannot have two copies of D allele. Hence, the genotype of the child can only be ppDd.

In order for the child to have blue eyes (pp), it means that the father has to have the non-pigmented allele (p). This also means that the father is heterozygous for eye pigmentation (Pp).

Hence, the genotype of the father is now limited to PpDD and PpDd.

the denominator has a very specific role.