Solve the blood grouping question: A man having blood group A marries with a woman having blood group O. They have a child. What will be the blood group of the child?
The man having blood group A possess two possibilities of antigen present in the blood: IAIA or IAIO
Similarly, the woman with blood group O has no antigen present in the blood: IOIO
The possible antigens present in the blood of their child is
IAIA X IOIO IAIO X IOIO
IAIO and IAIO IAIO and IOIO
Thus, if man is homozygous, with both dominant gene A present in the blood (IAIA), there is a 100% possibility that child will be heterozygous, with blood group A (Possessing antigen IAIO).
But, if the man is heterozygous, with blood antigen (IAIO), then the calculated possibility of blood group of child will be:
50% blood group A (with antigen IAIO) and 50% chance of blood group O (with no antigen IOIO)