A woman with blood type AB and a man with blood type O have three children, one of whom is adopted. The blood types of the children are A, B, and O. What is the blood type of the adopted child?

Question

Quizplus · Accepted Answer

A woman with blood type AB can pass either A or B alleles, and a man with blood type O can only pass O alleles. Therefore, their biological children can only have blood types A (AO) or B (BO). The child with blood type O (OO) must be adopted.

A Woman with Blood Type AB and a Man with Blood