On the other hand, if the gene is absent from that individual and the individual cannot synthesize either one of these Glycosyl transferases that can actually form these two types of linkages, then they're not going to be able to form the linkages and so they're going to have this molecule here, this glycoprotein. In that case they're the O blood type. So we see that a specific Glycoly transfer rates must be present in order to add an extra sugar to the galactose of the olymagride sequence. Oligosaccharide sequence, this for sugar sequence shown here. So a type A Glycosyl transferase is needed to add to an acetyl galactose while a type B Glycosyl transferase is needed to add the galactose to that oligosaccharide. And blood type O individuals basically have genes that cannot express either one of these type A or type B Glycosal transferase in which case they cannot form these bonds and so they end up having this glycoprotein on the red blood cell membrane.