In other species: olive baboon , pig , Japanese macaque , chimpanzee , Rhesus monkey , agile gibbon , common gibbon , siamang

Possibly relevant human trait(s) and/or gene(s) (MIM number): 110300 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal co-dominant

Considered a defect: no

Key variant known: yes

Year key variant first reported: 1998

Cross-species summary: Each blood group system consists of a set of blood types, each of which corresponds to a particular antigen (usually a glycoprotein) on the surface of red blood cells. The different types within a system are the result of the action of different alleles at a locus that usually encodes an enzyme that catalyses the creation of the feature of the glycoprotein unique to that type, e.g. the presence of a particular sugar at the end of a short chain of sugars. The ABO blood group system arises from two alleles at a locus that encodes a glycosyltransferase: the A allele encodes alpha 1-3-N-acetylgalactosaminyltransferase; and the B allele encodes alpha 1-3-galactosyltransferase. The B allele transferase catalyses the addition of galactose to a chain of four sugars attached to a protein known as H antigen. The A allele ltransferase catalyses the addition of a derivative of galactose called N-acetylgalactosamine to the same short chain of sugars. The third allele at this locus (the O allele) results in no sugar being added to the chain.

Molecular basis: Doxiadis et al. (1998) reported that the A and B alleles differ by just two missense mutations in codons 266 and 268. Thus allele A is a reflection of the peptide haplotype p.266Leu + p.268Gly, and allele B reflects the peptide haplotype p.266Met + p.268Ala.

Associated gene: