Question

A woman gives birth to a son who has type O blood. She has type B blood. Which of the following can be concluded from this about her parents' blood types? A.) One of her parents had at least one O allele. B.) One of her parents had two B alleles. C.) One of her parents had type B blood and the other type O blood. D.) One of her parents had type O blood.

Answer 1

The O allele (i) is recessive to the B allele (B), so the mother's genotype must be Bi (since she passes on the i allele to her son). In order for that to happen, one of her parents had to have at least one B allele and one i allele.
The answer is A.) One of her parents had at least one O allele.
The other answers are possible but not necessarily true.

Answer 2

The correct answer would be option A.

Explanation:

The allele for the O group is recessive to the allele of B blood group, so the genotype of the mother should be heterozygous with one allele of O and one allele of B blood group because the son has O blood group.

This condition is only possible if one parent of the mother had at least one allele of the O blood group to carry its next generation.

Thus, the correct answer would be option A.