Pyrimidine dimer

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Pyrimidine Dimer

Pyrimidine dimer (pronunciation: /pɪˈrɪmɪdiːn ˈdaɪmər/) is a molecular lesion formed from thymine or cytosine bases in DNA via photochemical reactions.

Etymology

The term "Pyrimidine dimer" is derived from the name of the Pyrimidine base, a heterocyclic aromatic organic compound, and the word "dimer", which refers to a molecule or molecular complex consisting of two identical molecules linked together.

Definition

A Pyrimidine dimer involves the abnormal covalent bonding of two adjacent pyrimidine bases, thymine or cytosine, in a DNA strand due to ultraviolet (UV) radiation. This results in a bulge or kink in the DNA strand, which can interfere with normal DNA replication.

Formation

Pyrimidine dimers are primarily formed through the action of ultraviolet B (UVB) radiation, which is absorbed by the DNA molecule, causing a chemical reaction that forms a covalent bond between two adjacent pyrimidine bases. This reaction can involve two identical bases (a homodimer) or two different bases (a heterodimer).

Repair

The repair of pyrimidine dimers is carried out by a process known as Nucleotide Excision Repair (NER). This process involves the removal of the dimer and the filling in of the resulting gap with the correct nucleotides by DNA polymerase.

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