The basic parts of RNA are the same than for DNA with two major differences. The pyrimidyne base uracil exchange thymine and ribose replace deoxyribose see the sugar, pyrimidines and purines pages. Uracil and Adenine for a base pair formed by two hydrogen bonds. It is must to note in which most RNA folding algorithms predict only secondary relatively than tertiary structure. The 3D shape of the molecule is significant to molecular function but is harder to predict. This is because tertiary structure is called from crystallography for only tRNA series as explained at the top of this page. Secondary structure is commonly considered a sufficient around, until more is called about tertiary structure of RNA.