A type A woman is the daughter of a type O father and a type A mother. If she has children with a type AB man, what is the probability of a type AB child?

Answer 1

25% probability, use a Punnett square.

Answer 2

The Type O father will only be able to donate an O allele. Since the daughter is Type A, that means her genotype must be AO. Then for the daughter's child, we can do the punnett square with AO and AB, which gives you a 25% chance that the child will be AB.