Similarities: - Both consist of a pentose sugar, a phosphate group and 4 nitrogenous bases.- Both are joined by covalent phosphodiester bonds between the phosphate and pentose sugar groups.Differences:- DNA has two strands of polynucleotides, which forms a double helix. RNA is linear and only has a single polypeptide strand.- RNA has the base uracil, DNA has the base thymine.- RNA has ribose sugar groups, DNA has deoxyribose sugar groups, which have one less hydroxyl group.- DNA is normally found associated with histone proteins to form nucleosomes, RNA is not bound to proteins in its native state.