TLDR: The ABO blood group system is a way to classify different types of blood based on the presence or absence of certain antigens on red blood cells. It is important for blood transfusions and can cause adverse reactions if there is a mismatch. The ABO blood types were discovered by Karl Landsteiner in 1901 and are also found in other primates. The blood types are inherited from both parents and can be classified as A, B, AB, or O. There are also subgroups within the A blood type. The ABO gene is located on chromosome 9 and controls the production of enzymes that modify the carbohydrate content of the red blood cell antigens. The distribution of blood types varies across different populations and there are theories about the evolutionary history of the ABO blood group system. The ABO antigens have roles in cell membrane integrity, cell adhesion, and acting as receptors for extracellular ligands. The ABO antigen is also expressed on the von Willebrand factor, which is involved in hemostasis. ABO blood group incompatibilities can cause hemolytic disease of the newborn. There are clinical applications and markers associated with the ABO blood group system, but some popular ideas, such as blood type personality theories and blood type diets, are not supported by scientific evidence.

Summary: The ABO blood group system is a way to classify different types of blood based on the presence or absence of certain antigens on red blood cells. It is the most important blood type classification system for human blood transfusions. A mismatch in blood types can cause adverse reactions or organ rejection. The ABO blood types were discovered by Karl Landsteiner in 1901 and are also found in other primates. They are inherited from both parents and can be classified as A, B, AB, or O. The ABO gene, located on chromosome 9, controls the production of enzymes that modify the carbohydrate content of the red blood cell antigens. The distribution of blood types varies across different populations and there are theories about the evolutionary history of the ABO blood group system. The ABO antigens have roles in cell membrane integrity, cell adhesion, and acting as receptors for extracellular ligands. The ABO antigen is also expressed on the von Willebrand factor, which is involved in hemostasis. ABO blood group incompatibilities can cause hemolytic disease of the newborn. There are clinical applications and markers associated with the ABO blood group system, but some popular ideas, such as blood type personality theories and blood type diets, are not supported by scientific evidence.

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• Antigen
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• Allele
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