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Thymine could also be a target for actions of 5-fluorouracil (5-FU) in cancer treatment. 5-FU can be a metabolic analog of thymine (in DNA synthesis) or uracil (in RNA synthesis). Substitution of this analog inhibits DNA synthesis in actively dividing cells. Thymine bases are frequently oxidized to hydantoins over time after the death of an ...
Methylation of cytosine to form 5-methylcytosine occurs at the same 5 position on the pyrimidine ring where the DNA base thymine's methyl group is located; the same position distinguishes thymine from the analogous RNA base uracil, which has no methyl group. Spontaneous deamination of 5-methylcytosine converts it to thymine. This results in a T ...
5-Methylcytosine (5mC) 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.
There are many laboratory synthesis of uracil available. The first reaction is the simplest of the syntheses, by adding water to cytosine to produce uracil and ammonia: [2] C 4 H 5 N 3 O + H 2 O → C 4 H 4 N 2 O 2 + NH 3. The most common way to synthesize uracil is by the condensation of malic acid with urea in fuming sulfuric acid: [5] C 4 H ...
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]
In enzymology, a methylenetetrahydrofolate-tRNA-(uracil-5-)-methyltransferase (EC 2.1.1.74) is an enzyme that catalyzes the chemical reaction 5,10-methylenetetrahydrofolate + tRNA containing uridine at position 54 + FADH 2 ⇌ {\displaystyle \rightleftharpoons } tetrahydrofolate + tRNA containing ribothymidine at position 54 + FAD
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).
Spontaneous deamination of 5-methylcytosine results in thymine and ammonia. This is the most common single nucleotide mutation. In DNA, this reaction, if detected prior to passage of the replication fork, can be corrected by the enzyme thymine-DNA glycosylase, which removes the thymine base in a G/T mismatch. This leaves an abasic site that is ...