So how exactly do these base pairs actually stack within the interior portion of our DNA molecule? Well, they are able to basically show that one purine always bonds to a single Pyridine and the other purine always binds to the other Pyridine. In DNA molecules, they are able to show that our guanine bonds with cytosine and adenine binds with thiamine. And these are the interactions that basically exist between our bases. So we have guanine forms three hydrogen bonds with cytosine. This is one, two, three, and adenine forms only two of these hydrogen bonds.