Answer
A brief explanation about the blood groups. As you probably know, a person’s blood type is determined by the ABO system. Everyone has 2 of these genes that together determine the blood group. You get one gene from each parent. A and B dominate above 0. If someone has blood group A, they can therefore have AA or AO at DNA level. Both are visible in the blood as A.
If the mother has blood group O, you definitely have OO at DNA level. The father has blood group B. He will probably have BO at DNA level. (BB is also possible, but since blood group B is not very common, it will probably be BO).
The mother will definitely pass an O to your children. The father will pass either a B or an O (assuming he is BO).
So there is a 50% chance of having a child with blood group O (if both have passed on the O), and a 50% chance of a child with blood group B (if the mother passed on the O and the father the B).
If the father would also have blood group 0, he will certainly pass on an O. All children will then have blood group 0.
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