ABO blood group system in blood type distribution within human subpopulations. In the UK, the distribution of blood type frequencies through the population still shows some correlation to the distribution of placenames and to the successive invasions and migrations including Norsemen, Danes, Saxons, Celts, and Normans who contributed the morphemes to the placenames and the genes to the population. The two common O alleles, O01 and O02, share their first 261 nucleotides with the group A allele A01. However, unlike the group A allele, a guanosine base is subsequently deleted. A premature stop codon results from this frame-shift mutation. This variant is found worldwide,
Human blood group systems Human blood group systems The term human blood group systems is defined by International Society of Blood Transfusion as systems in the human species where cell-surface antigens—in particular, those on blood cells—are "controlled at a single gene locus or by two or more very closely linked homologous genes with little or no observable recombination between them", and include the common ABO and Rh (Rhesus) antigen systems, as well as many others; thirty-five major human systems are identified as of November 2014. In addition to the ABO and Rh systems, the antigens expressed on blood cell membrane surfaces include 346 red