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ABO blood group

From SNPedia

The ABO blood group system is the best known blood typing system, determing blood group type as A, B, AB, or O, and thereby of importance for blood donors and recipients. Wikipedia

SNPs in the ABO gene determine ABO blood group type.

23andMe checks these 11 snps

However Determination of blood group type can be via genosets is shown in this spreadsheet or this more complicated and comprehensive one

The following are also SNPs in the ABO gene, used only to distinguish rare variants or to predict SNPs from the above list (based on linkage):

i4001527 or rs590787 are relevant to Rh+ or Rh-