Question

A father with type B blood and mother with type A blood have a child. Their child has discovered that her blood group is type O, during biology experiment at her school. Does she have any concerns about her parentage?

• A. Yes, because she should have type AB blood if they are her true biological parents
• B. No, because type O blood is possible if her parents both had genotye AB.
• C. No, because both of her parents could be heterozygous
• D. Yes, because both of her parents might be heterozygous
• E. No, because blood types A and B are codominant

Answer 1

The correct option is C No, because both of her parents could be heterozygous

ABO blood group is an example of codominance and multiple allelism wherein genotypes I${}^A$ I${}^O$ and I${}^A$ I${}^A$ gives A blood group. The possible genotypes of B blood group are I${}^B$ I${}^O$ and I${}^B$ I${}^B$. If father is heterozygous for B blood group (I${}^B$ I${}^O$) and mother is heterozygous for A blood group (I${}^A$ I${}^O$), their child can have O blood group. This is because of the presence of one copy of I${}^O$ allele in both parents. Thus, the correct answer is option C.