Now, what this means is at this particular locus on the chromosome, we have a specific sequence of nucleotides that codes for a special protein we're going to call protein A. And protein A will be found on the membrane of red blood cells. For this particular case, at this same locus, instead of having this sequence shown in red, we have a slightly different sequence of nucleotide shown in blue that codes for a different protein. We're going to call protein B that will be found on the membrane of the red blood cells. And the third allele basically means at the locus, we have a sequence of nucleotides that doesn't code for either one of these proteins. And so lowercase I is the allele that expresses neither protein A or protein B on the membrane of red blood cells.