There are ABO antigens, which designate ABO blood types. This is determined by the ABO gene. For example: There are also Rhesus (Rh) antigens, which determine if blood is "positive" or "negative." ...
It's a bit simplistic, but you can think of the Rh factor as a protein that is either present (positive) or absent (negative) on red blood cells. Exact percentages vary with race, but most people ...