Question

A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these three individuals? What genotypes, and in what frequencies would you expect in future offspring from this marriage?

Short answer

The genotypes of three individuals are I^Ai(man), I^Bi(woman), and ii(child). The future children with genotypes and frequencies are ¼ I^AI^B, ¼ I^Ai, ¼ I^Bi, and ¼ ii.

Step-by-step solution

Description of predictions of crossings

A man with type A blood group married a woman with type B. The child gets the blood group of O. It is due to the result of two recessive alleles.

The parents are heterozygous, so that that child will receive one recessive allele from the parents. The two blood group alleles in the man are IA and i., and that in the woman are IB and i.

Description of Punnet square for the given conditions

	IA	i
IB	IAIB	IBi
i	IAi	ii

Predictions of frequencies for future children

The Punnet square crossing results in the formation of four genotypic frequencies. The genotypic combinations of the different blood groups are IAIB, IBi, IAi, and ii.

Each of the genotypic combinations is one out of four varieties. The final frequencies of each genetic combination are ¼.

Hence, the man with blood group A and women with blood group B can have a child with blood group O with probability ¼.