So if we have this type of linkage and this type of additional sugar, that's the A. If we have this one, that's the B. If we have neither, then it's the O. So we see that all three antigens have the oligosaccharide sequence in common. Now what ultimately determines if an individual has one of these three types of antigens or if they have both of these antigens? Well, basically it's the genetic information in the DNA.