Why can't type O blood and type B blood produce offspring of type A blood? What is the genetic principle of blood type?
According to the law of human blood type inheritance, parents of type O blood and type B blood can only have offspring of type O blood or type B blood, and it is impossible to have offspring of type A blood.
We know that human blood types are mainly divided into O blood, A blood, B blood and AB blood. When giving blood to a patient, in principle, only the same type of blood can be transfused. It is possible to cause hemolytic transfusion reactions. Even if type O blood is known as the universal blood type, blood transfusions are only given to people with other blood types in emergency situations.
Humans have a total of 23 pairs of chromosomes. The ABO blood type gene is located on the ninth pair of autosomes and is controlled by three genes, A, B, and O. Therefore, there are six combinations of genes on this pair of chromosomes: AO, BO, AA , BB, AB, and OO, where A and B genes are dominant genes, and O genes are recessive genes, that is, when A or B genes exist, O genes will not be expressed.
Therefore, only when the OO gene exists at the same time, type O blood will appear, and both AO and AA are expressed as type A blood, and both BO and BB are expressed as type B blood; then for parents of type O blood and type B blood , Type O blood can only be a combination of OO, and blood type B may be BO or BB, which is impossible to contain A gene, so it is impossible to have offspring of type A blood and type AB, and the offspring can only be Blood type O or type B blood.
ABO blood type
Different blood group genes will eventually express different glycoproteins on red blood cells, platelets and various plasma cells, and have antigen specificity. If the blood of the recipient contains antibodies against the red blood cell-specific antigen of the donor, it will It can cause hemolysis, and this effect even exists between the mother and the fetus. In addition to the corresponding antigens, there are specific antibodies for each blood type, among which:
Type A blood: there are a antigens on the surface of red blood cells, and b antibodies in the blood;
Type B blood: There are b antigens on the surface of red blood cells, and there are a antibodies in the blood;
Type O blood: There is no a antigen or b antigen on the surface of red blood cells, and the blood has a antibody and b antibody;
Type AB blood: There are a and b antigens on the surface of red blood cells, and neither antibody is present in the blood.
In this way, it can be understood that type AB blood contains two antigens, so type AB blood cannot be transfused to people of any other blood type; and type O blood does not have both antigens, so it can be transfused to people of other blood types. The name of the universal blood type.
But type O blood also contains two kinds of antibodies, so when a small amount of blood type O is transfused to people of other blood types, the antibodies will be neutralized, but the red blood cells will not be attacked by the recipient's immune system. It can be used in emergency situations. In principle, clinical blood transfusion is still only given to people of the same blood type.
You may have heard of Rh-negative blood, also known as panda blood. In fact, apart from ABO blood, humans have found more than a dozen different blood types so far. Blood type is controlled by a pair of alleles, genes that express an antigen on red blood cells called Rh positive and vice versa.
Among the Chinese Han nationality, the proportion of Rh negative blood is only 3/1,000, and the RH blood type and ABO blood type are independent of each other. The matching of these two blood types needs to be considered during blood transfusion. At this time, the matching of RH negative blood will be more difficult. The RH negative of mutual blood transfusion is less than 3/10,000, so it is called panda blood.
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