Blood Groups:
- In human beings, blood varies from person to person on the basis of surface antigens on RBCS, blood can be divided into various groups.
- Antigens are also called as agglutinogen and they stimulate the formation of antibodies. Chemically, antigens are mucopolysaccharide (glycoprotein),
- Group “O” blood can be donated to persons with any other blood group and hence “O” group individuals are called ‘Universal donors’. Persons with “AB” group can accept blood from persons with AB as well as the other groups of blood. Therefore, such persons are called ‘Universal recipients’.

- The antibodies are also called agglutinin and are made up of globulin protein.
- There is a reaction between similar antigen & antibody which is called agglutination.
- It results in clumping of RBC which may be fatal.
There are two main systems to classify the human blood –
1. ABO System
2. Rh-system
1. ABO System:
It was discovered by Landstenier (1900).
- According to it, there are two types of natural antigens on the RBCs namely A and B. Similarity, two types of natural antibodies in the plasma namely anti-A or a and anti-B or b
2. Genetics of ABO System:
- Burn Stein (1924 – 25) First explained that ABO blood groups in human beings are a hereditary character.
- ABO system is controlled by three genes. Hence, it is an example of multiple gene inheritance.
