Red blood cells have agglutinogen antigens and agglutinin antibodies {blood type}|. Blood can have types O, A, B, or AB. If different types mix, they precipitate {agglutination}. Blood can have types M or N. Blood can have Rh factor in 85% of people, or not in 15% of people.
Red blood cells have antigens {agglutinogen} and antibodies {agglutinin}.
Blood groups {ABO blood group} can have type A, type B, type AB, and type O.
gene
Galactosyl transferase gene is on chromosome 9. A and B are co-dominant alleles. O is recessive allele.
diseases
Water-soluble galactosyl transferases can protect people from meningitis, yeast infections, and urinary tract infections but can increase influenza and respiratory synctitial virus. Cholera is highest in type O, middle in A and B, and lowest in AB, so A and B continue to exist {frequency-dependent selection}. Malaria is highest in types A, B, and AB and lowest in type O.
time
Perhaps, Type O is oldest, appearing 50,000 years ago. Perhaps, Type A appeared 25,000 years ago. Perhaps, type B evolved from type O 15,000 years ago. Perhaps, Type AB appeared 1000 years ago.
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Date Modified: 2022.0225