Two boys have blood group I (0) N iII (A) M, two women have IV (AB) M and II (A) MN. Determine who is whose son?

1) First, let’s define the genotypes of boys and mothers.

The first blood group is 00, the second is AA or A0, the third is BB or B0, and the fourth is AB.

MN groups are not associated with AB0.

The first boy has the genotype 00NN, the second – A * MM, in place * there can be both A and 0.

The first woman is ABMM, the second is AAMN or A0MN.

2) Determine what gametes women give,
First: AM, VM.

Second: AM, AN or AM, 0M, AN, 0N.

3) Both parents of the first boy must have 0N alleles, otherwise he will have a different blood type. Only the second woman is suitable for this condition, and then her genotype is A0MN.

Accordingly, the mother of the second boy has a fourth M group.