Question

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

Answer 1

Given:

• Child has blood group O
• Father has blood group A
• Mother has blood group B

To determine the possible genotypes of parents and offspring, we need to use the principles of Mendelian genetics and blood group inheritance.

The ABO blood group system is determined by the presence or absence of antigens A and B on the surface of red blood cells. There are three alleles for this gene: IA, IB, and i. The IA and IB alleles are codominant, while the i allele is recessive.

Possible genotypes for the parents:

• Since the child has blood group O, the child must have two copies of the i allele (ii).
• The father has blood group A, so he could have the genotype IAIA or IAi.
• The mother has blood group B, so she could have the genotype IBIB or IBi.

Possible genotypes for the offspring:

• Each parent can pass on one of their two alleles to their offspring.
• The possible genotypes of the father are IA and i, while the possible genotypes of the mother are IB and i.
• Therefore, the possible genotypes of the offspring are IAi, IBi, ii (which corresponds to blood group O).

In summary:

• Possible genotype for the father: IAIA or IAi
• Possible genotype for the mother: IBIB or IBi
• Possible genotypes for the offspring: IAi, IBi, ii (blood group O)