CBSE Class 10 Answered

Our red blood cells have antigens on their surface and the ability to form these antigens is governed by the genes inherited from the parents. The genotype of an individual decides the phenotype (blood group) of the individual.

In the ABO system, there are three alleles that occupy a specific position on a specific chromosome: I^A-producing antigen A, I^B- producing antigen B and I^O- producing neither antigen A nor antigen B. I^A and I^B are codominant, that is, if both the alleles are present, both the antigens will be formed on the surface of the red blood cells and the individual will have the blood group AB. I^O is recessive and produces neither antigen and so, the individual will have blood group O. The genetic make-up can have six possibilities resulting in the following phenotypes:

I^A I^B – AB, I^A I^A – A, I^A I^O- A, I^BI^B – B, I^BI^O – B and I^OI^O – O.