(D)RNA = (Deoxy)ribose nucleic acid It has 3 components: a nitrogenous base : purine (A,G) or pyrimidine (T,C) is linked at position 1 on a pentose sugar.a sugar : DNA has 2'-deoxyribose where as RNA has ribose (OH group at potition 2 on pentose ring).and a phosphate : The sugar can be linked by its 5' position to a phosphate group or 3' position to next nucleic acid's phosphate. (direction : 5' --> 3')*DNA contains A,G, C, T, while RNA contains A, G, C, U.