By Billie Rubin, Hemoglobin’s Catabolic Cousin, reporting from the labs of Stanford Blood Center
You may have heard of geometric shapes that are infinitely complex like clouds or snowflakes, but there’s also our complicated little ABO (blood group) system. The four major blood types, A, B, O and AB, are controlled by just one gene on chromosome # 9 and the version of that gene that is inherited from your parents determines your blood type.
Easy enough. But deep down in the DNA, slight changes or mutations in that one gene can lead to even more versions (alleles). For example, about 45% of us are type A, but type A also has some rare subtypes like A2 and A3. About 100 of those mutations have been identified in the ABO system alone.
Then, in the Rh system, which determines the + or following your blood type, 200 different mutations have been identified! And researchers aren’t sure they have found all of them yet. Fortunately, the testing the hospitals do can detect compatibility problems with very rare subtypes when they type the blood and test it with the patient’s blood before transfusing it.