And any given nucleotide consists of three sections. We have the sugar, the nitrogenous base and our phosphate group. And there are four different types of nitrogenous bases. The purines are adenine and guanine, while our perimeterines are thymine and cytosine. Now, the way that our two antiparall singlestranded DNA bonds together is via hydrogen bonds between our adjacent nitrogenous bases. So guanine nitrogenous base always forms bonds with cytotine while adenine always forms bonds with thymine.