Is this possible? (question about blood groups)?

Question

ok theres this old couple i know

his bloog group is O+

hers is AB+

two of their of children (out of 7) are O+

i dont know much about biology but i though that their children had to be either A or B nuh?

Answer 1

Biological children of such a union would have to be either A or B, yes--phenotypes AO or BO, to be precise.

I would suspect either mistaken information about the blood types, or else some of the children are adopted.  Even if the mother had become pregnant by another man, she still couldn't have type O children.  ;-)

Answer 2

Yes this is possible.

If we follows the straight rules of inheritance with the ABO system, this would not be possible but there are some rare cases when this happens.

A produces Antigen A and B produces Antigen B.

A and B are dominant to the O allele.

If the blood type is A, the genotype can be AA or Ao.

If the blood type is B, the genotype can be BB or Bo.

If the blood type is AB, the genotype can only be AB

If the blood type is O, the genotype should be oo.

The mother is AB so she is producing antigens A and B.

The father is O means he is producing neither antigen A nor B.

But there is a third factor to the production of these Antigens: it is the H antigen which is precursor to the A and B antigens. The A or B antigens are produced by modifying the H antigen inherited from the parents.

In some rare cases, the child inherits 2 recessive alleles of the H gene and becomes hh. In this case, Even if the child is A, B or AB, he will not be able to produce A or B antigens and will be considered as O.

This is known as the Bombay Phenotype because it was first discovered in Bombay, India.

So in your case, the children can actually be A or B but will be considered as O.

Even the father may not be a real O.