Mary has type A blood and her husband (John) has type B blood. John's parents both had type AB. Mary and John have three children, one with type A, one with type AB, and one with type B. Relatives suspect that one of the children was adopted.
(a)What are Mary and John's blood genotypes?
Mary's blood genotype is IAIA or IAi.
John's blood genotype is IBIB or IBi.
(b)Which child was adopted? Explain your answer.
None of their children are adopted.
Would you mind to review my answer and give me some comment? Please help me to explain for the part (b).