The woman has 4 blood group, the husband is the first and their son is also 4 to which of the parents

The woman has 4 blood group, the husband is the first and their son is also 4 to which of the parents this child is a step-child.

The blood group is determined by three alleles: A, B and 0.

Genotype 00 gives the first group,

AA, A0 – the second,

BB, B0 – third,

AB is the fourth.

Then the scheme for solving the problem looks like this:

Parents: AB x 00,

Gametes: A, B x 0,

Children: A0 (first), B0 (second). These are the groups that the joint children of these people will have.

A woman is a carrier of alleles that are necessary for the manifestation of 4 blood groups, a man does not have such. Accordingly, he is not the father of this child.