Karl Landsteiner was accredited Nobel Prize for the discovery of Blood group. He observed two different types of chemicals on the surface of the red blood cells. These chemicals were called antigens. Two different antigens were discovered and named as A and B. Two corresponding antibodies are also present in the plasma. Based upon the presence of A or B antigens he classified blood groups as A, B, AB and O.
Blood group is a genetically inherited trait. There are three alleles A, B and i. Blood group is determined by these three factors. 4 types of blood group can be formed by these alleles and they are:
1. Blood group A in which the allelic combination is either AA or Ai.
2. Blood group B in which the allelic combination is either BB or Bi.
3. Blood group AB in which the allelic combination AB.
4. Blood group O in which the allelic combination is ii.
A person who is going to receive blood has antibodies matching the donor blood's antigens, the red blood cells in the donated blood will clump. So , blood group has importance when blood tranfusions have to be performed.
AB+ blood group is universal acceptor.
O blood group is a universal donor because it can be donated to people with any other blood group. Basically O- blood group is a universal donor as O+ blood group cannot be donated to people with O- blood group.