The inheritance of blood groups
In all languages there are expressions in which family ties are related to having the same "blood", as when we speak of consanguinity to refer to people from the same family. But what is transmitted from parents to children is not the blood, but the genes that will determine their blood types and the rest of hereditary characteristics.
Human blood can be classified into different blood groups, currently more than 30 are known, although we will see the two most important systems.
AB0 system
Red blood cells (or erythrocytes) have proteins in their membrane that function as antigens. If a person receives blood with these antigens and their red blood cells do not have them, they will recognize them as something foreign to the body and their immune system will reject them, producing specific antibodies in their plasma that will neutralize them .
The inheritance of the blood groups of the AB0 system is one of the cases that seem to violate Mendel's laws, since it is a question of multiple allelism, since there are three different possible alleles ( IA, IB, I0) although each individual it can only have two of them, one on each chromosome of the pair in which they are located.
Of the three possible alleles, IA, IB, are codominant, while I0 is recessive. Thus, there are four different phenotypes that correspond to six different genotypes:
- Blood group A : IAI0, IAIA
- Blood group B: IBIB, IBI0
- Blood group AB: IAIB
- Blood group 0: I0I0
People in group 0 do not have any of these antigens on the membrane of their erythrocytes, so they can donate blood to people in all groups, since they will not create antibodies against them . Instead, they can only receive those of other individuals in group 0 .
Those of the group A and B can only receive blood from their own group and the group 0, and can donate to those of the AB group, since those of blood group AB not create antibodies or against A or against B .
People of group AB can receive blood from any group, but they can only donate to their own blood type.
| Genotype |
Phenotype |
Antigens |
Serum antibodies |
|
AA, A0 |
A |
A |
Anti-B |
|
BB, B0 |
B |
B |
Anti-A |
|
AB |
AB |
A and B |
None |
|
00 |
0 |
Ninguno |
Anti-A and Anti-B |
Grupos sanguíneos. (s. f.). Recuperado 5 de marzo de 2016, a partir de http://salud.ccm.net/faq/12346-grupos-sanguineos