ABO blood group system gives type O. As both "I" and "I" are dominant over "i", only "ii" people have type O blood. Individuals with "II" or "Ii" have type A blood, and individuals with "II" or "Ii" have type B. "II" people have both phenotypes, because A and B express a special dominance relationship: codominance, which means that type A and B parents can have an AB child. A couple with type A and type B can also have a type O child if they are both heterozygous ("Ii","Ii"). The "cis-AB" phenotype has a single enzyme that creates both A and B antigens.
Blood type personality theory Dr LAURENT: "4groupes sanguins, 4 personnalités" Marco Pietteur ed. 2007/2014. Belgium. (In French) Blood type personality theory A pseudoscientific belief exists in some East Asian countries, that a person's ABO blood type is predictive of a person's personality, temperament, and compatibility with others. This superstition is similar to how astrological signs are perceived as influencing factors in a person's life in other countries. One of the reasons Japan developed the blood type personality indicator theory was in reaction against ethnic stereotypes coming from Europe. The popular belief originates with publications by Masahiko Nomi in the 1970s. The scientific community generally