The ABO blood group is transmitted in humans as follows: The A and B alleles are dominant to the O allele but codominant with each other. The O phenotype (OO genotype) is known as the "universal donor" in small-volume blood transfusions, whereas the AB phenotype (AB genotype) can be considered a "universal recipient". A man with blood type A mates with a woman with blood type B. Their child could have what possible blood type?

1) If the man is AA and the woman BB, the child can only be AB.

2) If the man is AA and the woman BO, the child could be either AB or AO (type A blood).

3) If the man is AO and the woman is BB, the child could be either AB or BO (type B blood).

4) If the man is AO and the woman is BO, the child could have all four possible blood types: AB, AO, BO or OO.

Explanation:

The possible genotypes and phenotypes of the ABO blood group are:

AA or AO: type A blood BB or BO: type B blood AB: type AB blood OO: type O blood

A man with blood type A mates with a type B blood woman.

The man could be either AA or AO. The woman could be either BB or BO.

1) If the man is AA and the woman BB, the child can only be AB.

2) If the man is AA and the woman BO, the child could be either AB or AO (type A blood).

3) If the man is AO and the woman is BB, the child could be either AB or BO (type B blood).

4) If the man is AO and the woman is BO, the child could have all four possible blood types: AB, AO, BO or OO.