Blood type is the classification of blood based on the presence of antibodies and genetic antigenic substances on the surface of red blood cells in the plasma.
Blood type is hereditary and represents the genetic inheritance of both parents. The two most important blood group systems are the ABO system and the Rh system.
ABO blood group system
The ABO system defines four blood types:
A - Antigens present on cells and anti B antibodies present in plasma;
B - The plasma contains B antigen and anti A antibodies;
• O - no antigen, but both anti A and anti B antibodies are present in the plasma;
AB - Contains both A and B antigens, but there are no antibodies in the plasma.
In genetics, blood type genes have two alleles, each with genotype A, B, or O. A and B are explicit, while O is implicit. So the combination of allele A and allele O is type A. Similarly, BO is type B, AA is type A, BB is type B, OO is type O, and AB is type AB.