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: IA-producing antigen A, IB- producing antigen B and IO- producing neither antigen A nor antigen B. IA and IB 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. IO 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:
IA IB – AB, IA IA – A, IA IO- A, IBIB – B, IBIO – B and IOIO – O.
Blood group of parents |
Blood group of child |
A and A |
A, O |
A and B |
A, B, AB, O |
A and AB |
A, B, AB |
A and O |
A, O |
B and B |
B, O |
AB and AB |
A, B. AB |
AB and O |
A, B |
O and O |
O |
In addition to the current practice of serologic testing of blood types, the progress in molecular diagnostics allows the increasing use of blood group genotyping. Genotyping allows the prediction of a phenotype based on the knowledge of the molecular basis of the currently known antigens. This allows a more detailed determination of the blood type of an individual.
Thus, it is possible to determine the blood group of a child through genetic inheritance if the blood groups of the parents are known.