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@.