Answer: Jack has the genotype Bo; Jill is AB; Jack's mother is OO.
Explanation: In the ABO blood type, the alleles A and B are dominant over O. However, the allele A is co-dominant with the allele B. That means an individual can have a genotype AB, which is Jill's case: her blood type has the two allele. For Jack's mother, her blood type is O. As O is recessive, her genotype will be OO, indicating the recessiveness. For Jack, his mother is recessive, so he will have genotype heterozygous for blood type B, which means BO.