Breakdown of the blood groups
There are several antigenic systems that allow us to identify the blood cells. The best known are the ABO and Rh systems which define the compatibility and the incompatibility of the blood between the donor and the recipient.
The ABO system assigns each individual a letter which specified his blood group: A, B, AB or O. The Rh system establishes whether you are Rh positive or Rh negative.
In the Caucasian population (people with European traits and a light skin), the various blood types are broken down as follows: