A man with blood group A married a woman with blood group B. they have a son with AB blood group and a daughter with blood group O. Work out the cross and show the possibility of such inheritance.

Since the said parents have a daughter with O blood group, we can assume that both parents are heterozygous.

Hence,

 Man with type A blood group has the genotype: AO

 Woman with B blood group has the genotype: BO.

The blood types of their children:

1/4 will be AB-  AB Blood group.

1/4 will be AO - A Blood group.

1/4 will be BO -  B Blood group.

1/4 will be OO-  O Blood group

Parents:           Heterozygous A Blood Father            X          Heterozygous B Blood Mother         

Alleles                                          I^A  i                    X                         I^B  i

F1  progeny               I^A  i                                      I^A  I^B                     I^B  i               ii