Figure 1From: DNA nanotechnology: a future perspectiveBasic DNA structure proposed by Watson and Crick. DNA is made up of two kinds of nitrogenous bases, purines (adenine and guanine) and pyrimidines (thymine and cytosine). Purine bases bind only to their respective pyrimidine bases, i.e., adenine always pairs with thymine, while guanine binds to cytosine [3].Back to article page