Question

Two parents think their baby was switched at the hospital. It's 1968 so fingerprinting technology does not exist yet. The mother has the blood type "O," the father has the blood type "AB," and the baby had the blood type "B". Based on the information, which of the following is the most likely explanation?

A) The baby was switched.
B) The baby's blood type could result from the parents' blood types.
C) The hospital made an error in recording the baby's blood type.
D) The baby's blood type is impossible given the parents' blood types.

Answer 1

A baby can have blood type B if one parent has blood type O (genotype ii) and the other has blood type AB, since the baby can inherit an 'i' allele from the O parent and a 'B' allele from the AB parent.

Step-by-step explanation:

The blood type of a baby with parents having blood types O (genotype ii) and AB can indeed be type B. In this case, the mother with blood type O can only pass an 'i' allele to her offspring, as she would have a genotype of ii. The father with blood type AB has one A allele and one B allele to contribute. When the mother contributes an 'i' allele and the father contributes a 'B' allele, the resulting genotype for the baby would be 'iB', which phenotypically expresses as blood type B. Hence, the correct answer to your question is B) The baby's blood type could result from the parents' blood types.