a man having blood group o marries awoman having blood group b and they have a daughter. what will be the blood group of the daughter?

Question

valentina613 · Answer

The woman will give off either an A or a B allele to her child; the man can only give off an O because that is all he has. So if the A is given from the woman, it will be AO, forcing the A to show. If a B is given from the woman, it will be BO, forcing the B to show. The child has a 50-50 shot at either being AO (A shown), or BO (B shown). There is no chance at being AB or O.

frostbite · Answer

Unfortunately not entirely correct, you do however got into the point that the case is more complicated than at first sight.

First of all we gotta find out the potential genotypes of the man and woman:

The man is very simple as we know that in order to have the blood type 0 you got to be homozygous recessive for the 0-allele.

The woman is a bit more difficult. As we only know she is having blood type B and got no information about her ancestors, there are two possible combinations:
1) homozygous dominant for the B-allele
2) hetrozygous dominant for the B-allele

As the woman can have two possible genotypes we test them both in our square:

Case 1 (homozygous dominant for the B-allele):
|dw:1415670133651:dw|
As we see there is a 100% chance for their daughter to be hetrozygous and get the B blood type.

Case 2 (hetrozygous dominant for the B-allele):
|dw:1415670359777:dw|
As we can see there is a 50% chance for their daughter to be homozugous for the 0-allele and 50% chance of being homozygous for the B-allele.