Exemplar Problems

Question:

A child has blood group O. If the father has blood group A and the mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offspring.

Answer:

The child’s blood group O indicates that they have two O alleles (OO genotype).

To determine the genotypes of the parents:

Since the father has blood group A, he can have genotype AA or AO. Since the mother has blood group B, she can have genotype BB or BO.

Possible genotypes of the parents:

Father’s genotypes: AA or AO Mother’s genotypes: BB or BO

Possible genotypes of other offspring:

If the father is AO and the mother is BO:

Offspring can have genotypes AO (blood type A) or OO (blood type O).

If the father is AA and the mother is AO:

Offspring will have genotypes AO (blood type A) or AA (blood type A).