The substitution of a purine for a pyrimidine, or vice versa is a transversion. 嘌呤为嘧啶取代或嘧啶为嘌呤所取代，叫做颠换。
The relative merits between "degradable" and "non-degradable" radiolabeled pyrimidine analogues have been compared in this paper. 本文比较可分解及不可分解放射性标帜嘧啶核苷酸之个别优点。
