Mendelian trait/disorder: yes

Considered a defect: yes

Key variant known: no

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.

Species-specific symbol: X

Species-specific description: This locus has at least 2 alleles.