The Role of Alleles in Blood Types

So the cases i just talked about are cases in which these alleles have a relationship called complete dominance so one phenotype or one genotype is dominant over there. However you can have codominants as well so for codominant traits the heterozygous genotype shows both phenotypes. A good example of this comes in the form of how blood types work because when you have  alleles A and B you are going to have both those antigens on your surface. For blood type O though however has no antigen on its surface so that's the universal universal accepted or universally donated blood anybody can have transfused into them due to their body having no antibodies against red blood cells.