Many people know what their blood type is and understand that blood types must be matched in a medical emergency. The ABO blood group is the most significant blood factor in clinical applications involving blood transfusions. Understanding the importance of the ABO blood group is not limited to clinical applications, however. With our recent ability to rapidly sequence genes, the ABO blood group is also proving to be a valuable asset for determining human migration patterns and origins.
What Determines Blood Type?
ABO blood types are determined by a cell surface marker that identifies the cell as belonging to "self" or to that individual. These cell surface markers are characterized by a protein or lipid that has an extension of a particular arrangement of sugars. Figure 1 shows the arrangement of sugars that determines each of the A, B, and O blood types.1 Note that each is identical, except that types A and B have an additional sugar: N-acetylgalactosamine for A, and galactose for B.