A nucleotide is composed of a nitrogenous base, a sugar, and a phosphate group. In ribonucleotides, the sugar is ribose, while in deoxynucleotides, the sugar is deoxyribose. Adenine, guanine, and cytosine are nitrogenous bases in both DNA and RNA, while thymine is found only in DNA and uracil is found only in RNA.Nov 26, 2011