The second important difference is the presence of the nitrogenous base uracil (abbreviated 'U'). Uracil does not exist in DNA. Like DNA, RNA contains cytosine (C), guanine (G), and adenine (A); however, in RNA, uracil (U) takes the place of thymine (T) that exists in DNA. Uracil will act in a similar way to thymine in that it can bind to adenine. The four nitrogenous bases of DNA are A, T, C, and G; while in RNA they are A, U, C, and G.