Question

A person that is heterozygous type A (AO) marries a person that is heterozygous type B (BO).

Answer 1

The right answer is 25%

The offsprings are: AO, OO, AB, BO .

Red blood cells with phenotype O can only correspond to a single OO genotype, but to phenotype A can correspond homozygous AA or heterozygous AO subjects. Phenotype B may also correspond BB homozygotes or BO heterozygotes. On the other hand, subjects AB are necessarily heterozygous, having inherited an allele A and a allele B.

Answer 2

     A     O
B  AB   BO
O  AO  OO 

25%