And then we use X ray order radiography to basically determine exactly where those radioactively labeled fragments actually were. And so this is the diagram that we get. Now, how can we use this to actually determine what the sequence of that initial DNA molecule is? Well, we know what the first three nucleotides are because that's the primer. So we have T, G and C. So the question is, what are these remaining nucleotides here? Well, let's try to use the following setup to base determine what the sequence is.