Why do people have different blood types?

Today's google doodle commemorates Austrian doctor Karl Landsteiner (Karl Landsteiner), who was the first to discover that humans have different blood types, a discovery that also lays the foundation for a safe blood transfusion system. In 1930, he won the Nobel Prize in Physiology for it.

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Let's talk a little bit about blood type today. What we are most familiar with is the ABO blood type in the picture, but in addition, there are actually many other blood typing methods, such as Rh blood type, MNSs blood type and so on.

the ABO blood group system is discovered by mixing the blood of different people with each other, which produces different results: some are at peace, others cause clots. In fact, it can also be learned in biology textbooks, this is because there are different antigens on red blood cells of different blood types, and different antibodies in serum. If the antigen and the corresponding antibody meet together, there will be an agglutination reaction.

our medical students will do this agglutination experiment to identify blood groups in physiology experiment class, that is, to take some of their own blood to observe the reaction in the serum containing anti-A, anti-B and anti-A + anti-B. I have type O blood, so the result is that there are no phenomena in all three. In order to see the phenomenon, we have to tie the students with type AB blood one after another.

the "base" of this blood group antigen on red blood cells is H antigen, and according to the difference of genes, different antigens will be attached to this substrate: an antigen corresponding to A gene and B antigen corresponding to B gene. O gene does not produce obvious antigenicity. As for their genetic laws, I believe I don't have to tell them any more (it is said that a lot of dog blood stories have been pulled out from the blood type.

so, why on earth are there different blood types? The most straightforward answer, of course, is the mutation. The difference in ABO blood group comes from different mutated versions of the same locus. However, from an evolutionary point of view, there is no particularly clear explanation for this problem.

these blood group antigens on red blood cells do not seem to be necessary for human survival. Not only do people with blood group O who lack An and B antigens live well, but there are even some\ & quot; Bombay blood groups\ & quot;. Ten percent of people don't even have a "basal" H antigen, and there's nothing wrong with their health (although this rare condition can be troublesome during blood transfusions, and people of the Bombay type can only receive blood from other Mumbai types).

some scientists believe that the significance of blood type diversity may be to enable human beings to better adapt to different environments. There are some differences in disease susceptibility among people with different blood types, that is, different blood types may reduce people's risk of developing different diseases. For example, some studies have suggested that type O blood is more conducive to the fight against malaria.

there are also many unscientific theories around ABO blood type, such as blood type corresponding to personality, or people of different blood types should eat different foods, which have no scientific basis. How many mosquitoes people have actually has little to do with blood type.

read the original text to learn the story of Rh blood type, which are the two most important blood types in medicine.