What is the blood group of children whose parents have II and III blood groups?

The second and third blood groups, according to Landsteiner’s classification, are designated by the letters A and B. Each group has its own specific antibodies, the genes of which are dominant. Given that there are two DNA strands, the following genetic variants are possible for these blood groups:

Group II – AA, A0

Group III – BB, B0

Consider the case when both parents are heterozygotes (A0; B0). In this case, children with any blood group (IV – AB; III – B0; II – AO; I – 00) can be born with an equal probability of 25%.

In the case when both parents are homozygous (AA; BB), then with a 100% probability, children with IV blood group will be born.

If one of the parents is homozygous for Group II (AA), and the other is heterozygous (B0), a child with Group IV will be born with a 50% probability, and a child from Group II with a 50% probability.

A similar situation is with homozygosity for group III (BB) and heterozygosity for II (AO): 50% – group IV; 50% – III group.