Question

Part a in a disputed parentage case, the child is blood type o, while the mother is blood type
a. what are the possible blood type(s) for the father

Answer 1

Child type o => genotype oo
mother type A => genotype AA or Ao
AA would not have given birth to type o (genotype oo), mother must have genotype Ao.

So father must contribute to the other o allele, so possible genotypes are:
Ao, Bo or oo.

Therefore the father's possible phenotypes are type A, type B or type O.