So this base could be Adamine, it could be Guanine, it could be Cytosine, or it could be Thymine. And so we have four different types of Ggntp molecules. And in step two, we have to add a tiny amount, about 1% with respect to the other nucleoside triphosphates of a specific dig deoxy nucleuside triphosphate. So we don't add all four types, we only add one type. Now, why is that important? Well, let's see what that actually does by examining the following diagram.