Editing Mutation (section)

=== Errors introduced during DNA repair ===
{{See also|DNA damage (naturally occurring)|DNA repair}}
Although naturally occurring double-strand breaks occur at a relatively low frequency in DNA, their repair often causes mutation. [[Non-homologous end joining]] (NHEJ) is a major pathway for repairing double-strand breaks. NHEJ involves removal of a few [[nucleotide]]s to allow somewhat inaccurate alignment of the two ends for rejoining followed by addition of nucleotides to fill in gaps. As a consequence, NHEJ often introduces mutations.<ref>{{cite journal | vauthors = Lieber MR | title = The mechanism of double-strand DNA break repair by the nonhomologous DNA end-joining pathway | journal = Annual Review of Biochemistry | volume = 79 | pages = 181–211 | date = July 2010 | pmid = 20192759 | pmc = 3079308 | doi = 10.1146/annurev.biochem.052308.093131 }}</ref>
[[File:Benzopyrene DNA adduct 1JDG.png|thumb|right|250px|A [[covalent]] [[adduct]] between the [[(+)-Benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide|metabolite]] of [[Benzo(a)pyrene|benzo[''a'']pyrene]], the major [[mutagen]] in [[tobacco smoking|tobacco smoke]], and DNA<ref>Created from [http://www.rcsb.org/pdb/explore/explore.do?pdbId=1JDG PDB 1JDG] {{webarchive|url=https://web.archive.org/web/20151231235020/http://www.rcsb.org/pdb/explore/explore.do?pdbId=1JDG |date=31 December 2015 }}</ref>]]