In human blood types, Rh positive is a trait that shows simple dominance over Rh negative. A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Which of the following phenotypes is possible for the father?
A) A negative
B) O negative
C) B positive
D) AB negative

Question

Quizplus · Accepted Answer

Since the mother is type A positive, she must have at least one dominant A allele and one positive Rh allele. The daughter is type O positive, which means she has two recessive O alleles and one positive Rh allele inherited from the mother. The son is type B negative, which means he has one B allele and two recessive Rh negative alleles. The only way for the father to have children with both B and O blood types is if he has at least one B allele and one O allele. Therefore, he could be type B positive, B negative, or O positive. Of these options, only option C (B positive) is listed.

In Human Blood Types, Rh Positive Is a Trait That