First question is what exactly determines the difference between these different blood types? And more specifically, what determines the blood type of any given individual? Because any given individual can only have one of these four different types of blood groups. Now, it turns out that on chromosome nine of our Carreotype, we basically have the allele the gene that codes for a special protein membrane that is found on red blood cells. So each human inside our DNA, we have a gene that codes for this protein. Now, before the protein is actually attached onto the membrane of red blood cells, it is modified in the Golgi apparatus and a carbohydrate attachment is made onto that protein to form a glycoprotein.