What is Thymine?

Thymine is an organic compound of the pyrimidine family, which is a constituent of deoxyribonucleic acid (DNA).  Thymine is one of the nitrogenous bases used to build nucleic acids. Along with cytosine, it is one of the two pyrimidine bases found in DNA. In RNA, it is usually replaced by uracil, but transfer RNA (tRNA) contains trace amounts of thymine.

Thymine Function

Thymine is one of the five primary (or canonical) nucleobases; the others are cytosine, uracil, guanine, and adenine. They are the fundamental nucleobases that make up the genetic code.  In RNA, thymine is replaced by the nucleobase called uracil, which is a methylated version of thymine. The presence of uracil in DNA could cause various complications during DNA replication due to its cytosine's ability to spontaneously deaminate into uracil. This leads to the excision of uracil from DNA, so, if uracil was present in DNA as a code, it would be excised, which would cause the loss of genetic information. RNA is a short-lived molecule, therefore, uracil's presence is more beneficial there.