Guanine: organic compound of the purine family often called a base consisting of two rings each containing both nitrogen and carbon atoms and an amino group.
鸟嘌呤：嘌呤类的有机化合物，常称为碱基，包含二个环，各含氮原子和碳原子，还有一个氨群。
2
Cytosine organic compound of the pyrimidine family often called a base consisting of a single ring containing both nitrogen and carbon atoms and an amino group.
胞嘧啶：嘧啶族的有机化合物。常被称为基，包含一个单环，内有氮原子和碳原子，还有氨群。
3
Thymine: Organic compound of the pyrimidine family, often called a Base, consisting of a ring containing Both nitrogen and carbon atoms, and a methyl group.