Have you ever wondered why we have different blood?

That blood from different people and different animals, learned immediately. In the XVII century, people who suffered from mental illness were transfused blood of lambs. The implication was that so people calm down. The desired effect was achieved: people calmed down once and for all. When the number of victims became too high, the practice was decided to stop.

In the nineteenth century in England began to pour blood from person to person. But it still did not lead to anything good.

A little later, the doctor Karl Landsteiner, drew attention to one thing. If you connect the red blood cells of one person with the blood serum of another (that is, its liquid part), sometimes red blood cells are collected in clots. And sometimes not. Landsteiner did a number of studies and identified three blood types. For this, by the way, the doctor received the Nobel Prize. Four same blood group proposed to classify different doctor, Jan Jansky.

Inside each red blood cell contains hemoglobin protein. It combines with oxygen and transports it to the organs of the body. Outside the erythrocyte contains a membrane, which consists of an antigen. Antigens interact with white blood cells — leukocytes. Antigens are the identification signs of the body. On them leukocytes recognize their red blood cells and do not try to attack them.

In human erythrocytes can be two types of antigen — A and B. Antigens are encoded alleles — different forms of the same gene. Is allele A, allele B and allele 0 (zero).

We inherit antigens from our parents. Like any genes, antigens are dominant and recessive. If the parents have the same blood type, the child will be the same. If the parents are carriers and antigen A, and antigen B, the child will AB blood group, that is IV. This is due to the fact that both antigen A and antigen B are dominant.

A null allele is recessive. Therefore, the first group of blood can be obtained only if both parents have the same first group of blood.

It turns out that there is I blood group (zero allele), II blood group (allele A), III blood group (allele B), the fourth blood group (alleles A and B).

If you pour a person with a third group of blood group four, the body will begin to rebel, as antigen A will be alien to him. However, the person with the fourth blood group it is possible to have a blood transfusion. The second and third group.

The blood of the first group can be transfused to all, as it has no antibodies. In this case, a person with the first group of blood can be transfused only the same blood.