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Question
A child has blood group O. If the father has blood group A and the mother has blood group B, work out the genotypes of the parents and the possible genotypes of the other offspring.
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Solution
If the father has blood group A, i.e., IAIA (homozygous), and the mother has blood group B, i.e., IBIB (homozygous), all offspring will have blood group AB (IAlB) rather than blood group O.
A child has blood group O only if both parents are heterozygous, i.e., father IAIi and mother IBIi.
Therefore, the parents of a child with blood group O will have genotypes IAi and IBi. A side from O blood group offspring, the child could have one of three other blood groups. They are IAi (blood group A), IBi (blood group B), and IAIB (blood group AB).
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