nucleotide bases

https://doi.org/10.1351/goldbook.N04254
The heterocyclic pyrimidine and purine compounds which are constituents of all @N04245@. Adenine (A), guanine (G) and cytosine (C) are found in both @D01597@ and @R05386@, thymine (T) is found (primarily) in @D01597@ and uracil (U) only in @R05386@.
Source:
PAC, 1992, 64, 143. (Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)) on page 147 [Terms] [Paper]