Difference Between Thymine and Uracil

Thymine vs Uracil

The nucleic acids contain chains of nucleotides. Each nucleotide comprises a nitrogenous base, a pentose sugar and a phosphate group. Nitrogenous bases make the backbone of the nucleic acids. Nitrogenous bases are mainly divided into two types; (a) pyrimidines, which include cytosine, uracil and thymine, and (b) purines, which include adenine and guanine. These bases exhibit specific base pairings; adenine always pairs with thymine (in DNA) or uracil (in RNA) while guanine pairs with cytosine. There are hydrogen bonds between every base pair that help to hold the bases together.


Thymine is one of the four nitrogenous bases needed to make the backbone of the DNA molecule. It is always paired with adenine by two hydrogen bonds. Thymine is a pyrimidine that is found only in DNA molecules and is synthesized from uracil.


Uracil is a pyrimidine type nitrogenous base that is found only in RNA molecules. It always pairs with adenine. Chemical difference of uracil and thymine is very small. Uracil has a hydrogen atom at C-5 carbon while thymine has a methyl group at the same carbon.

What is the difference between Thymine and Uracil?

• DNA molecules contain thymine, whereas RNA contain uracil.

• Thymine contains a methyl (CH3) group at number-5 carbon, whereas uracil contains hydrogen (H) molecule at number-5 carbon.

• In all biological systems, thymine is mainly synthesized from uracil.

• Ribonucleoside of the thymine is thymidine, whereas that of uracil is uradine.

• Deoxyribonucleoside of the thymine is deoxythymidine, whereas that of uracil is deoxyuridine.