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As its alternate name (5-methyluracil) suggests, thymine may be derived by methylation of uracil at the 5th carbon. In RNA, thymine is replaced with uracil in most cases. In DNA, thymine (T) binds to adenine (A) via two hydrogen bonds, thereby stabilizing the nucleic acid structures. Thymine combined with deoxyribose creates the nucleoside ...
The chemical compound 5-methyluridine (symbol m 5 U or m5U), also called ribothymidine (rT) [footnote 1], is a pyrimidine nucleoside. It is the ribonucleoside counterpart to the deoxyribonucleoside thymidine, which lacks a hydroxyl group at the 2' position. 5-Methyluridine contains a thymine base joined to a ribose pentose sugar. [4] It is a ...
5-Methylcytosine is a methylated form of the DNA base cytosine (C) that regulates gene transcription and takes several other biological roles. [1] When cytosine is methylated, the DNA maintains the same sequence, but the expression of methylated genes can be altered (the study of this is part of the field of epigenetics). 5-Methylcytosine is incorporated in the nucleoside 5-methylcytidine.
In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine. Uracil is a common and naturally occurring pyrimidine derivative. [2] The name "uracil" was coined in 1885 by the German chemist Robert Behrend, who was attempting to synthesize derivatives of uric acid. [3]
Instead of thymidine, RNA contains uridine (uracil joined to ribose). Uracil is chemically very similar to thymine, which is also known as 5-methyluracil. Since thymine nucleotides are precursors of DNA (but not RNA), the prefix "deoxy" is often left out, i.e., deoxythymidine is often just called thymidine. Thymidine is listed as a chemical ...
Cytosine can also be methylated into 5-methylcytosine by an enzyme called DNA methyltransferase or be methylated and hydroxylated to make 5-hydroxymethylcytosine. The difference in rates of deamination of cytosine and 5-methylcytosine (to uracil and thymine) forms the basis of bisulfite sequencing. [8]
Thymine and uracil are distinguished by merely the presence or absence of a methyl group on the fifth carbon (C5) of these heterocyclic six-membered rings. [2] [page needed] In addition, some viruses have aminoadenine (Z) instead of adenine. It differs in having an extra amine group, creating a more stable bond to thymine. [3]
Very short patch (VSP) repair is a DNA repair system that removes GT mismatches created by the deamination of 5-methylcytosine to thymine.This system exists because the glycosylases which normally target deaminated bases cannot target thymine (it being one of the regular four bases in DNA).