Question

A man with blood group A is married to a woman with blood group B and has a son with AB blood group and daughter with O blood group . Workout a cross for such a kind of inheritance.

Answer 1

Dear Student,

In the ABO system of blood group, A and B are the co-dominant alleles while O is the recessive one. This means that A and B alleles will express themselves whenever they are present. So, A, B and AB are the dominant blood groups. The child possessing the O blood group needs to have two O alleles. Thus, O is the recessive blood group. As given the son has blood group AB and the daughter has blood group O, this implies that all three types of alleles are present in parents. Such Inheritance is only possible when both the parents are heterozygous, then the possible genotype of man will be I^A i and that of female will be I^B i.

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

Father/Mother	A	O
B	AB - SON	BO
O	AO	OO - DAUGHTER

Regards

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