Question

Children have A and B types of blood. What are the blood types of parents not possible?
A. A and O
B. AB and O
C. AB and A
D. A and B

Answer 1

Rh factor is a protein present on the surface of the red blood cells. If the blood has a high amount of protein then it is Rh positive and if it lacks in protein then it is Rh negative blood type. Rarest blood group is AB negative and B negative. O blood groups are not the Rh type because it doesn't contain A and B markers. So genotypes determine the blood types.

Complete answer:
Option A: The parents who have A and O blood type will produce the children having blood type of A and O. So they can't produce the children having A and B.
So option A is the correct answer.
Option B: If the children have A and B blood type then the parents have AB and O blood type. So they produce the children who have A and B.
So Option B is not the correct answer.
Option C: The parents having AB and A blood type have the A, B and AB blood type of children. So the children have A and B type of blood.
So option C is not the correct answer.
Option D: A and B blood type of parents having A, B, O and AB type of blood in children.
So option D is not the correct answer.

Note:
The blood type of children depends on the genotype or DNA. The genotypes are AO, AB, BO and OO. The universal red cell donor has O negative type of blood. The universal plasma donor has AB type of blood. O negative is called the universal donor because the blood doesn't contain any antigen in it. After the ABO system Rh is the second most important system to determine blood type.