| PubChem = | SMILES = CC1=CNC(=O)NC1=O | MeSHName = Thymine }} | Section2 = | Section3 = }} Thymine's one of the four bases in the nucleic acid of DNA that make up the letters GCAT. The others are adenine, guanine, and cytosine. Thymine (T) always pairs with adenine. Thymine's also known as 5-methyluracil, a pyrimidine nucleobase. As the name suggests, thymine may be derived by methylation of uracil at the 5th carbon. In RNA, thymine's replaced with uracil in most cases. In DNA, thymine(T) bi… (More on Thymine)