Editing Mutagen (section)

==Effects==
{{main|Mutagenesis }}
Mutagens can cause changes to the DNA and are therefore [[Genotoxicity|genotoxic]]. They can affect the transcription and replication of the DNA, which in severe cases can lead to cell death. The mutagen produces mutations in the DNA, and deleterious mutation can result in aberrant, impaired or loss of function for a particular gene, and accumulation of mutations may lead to cancer. Mutagens may therefore be also carcinogens. However, some mutagens exert their mutagenic effect through their metabolites, and therefore whether such mutagens actually become carcinogenic may be dependent on the metabolic processes of an organism, and a compound shown to be mutagenic in one organism may not necessarily be carcinogenic in another.<ref>{{cite journal | vauthors = Allen JW, DeWeese GK, Gibson JB, Poorman PA, Moses MJ | title = Synaptonemal complex damage as a measure of chemical mutagen effects on mammalian germ cells | journal = Mutation Research | volume = 190 | issue = 1 | pages = 19–24 | date = January 1987 | pmid = 3099192 | doi = 10.1016/0165-7992(87)90076-5 | display-authors = 3 }}</ref>

Different mutagens act on DNA differently. Powerful mutagens may result in chromosomal instability,<ref>{{cite journal | vauthors = Huang L, Snyder AR, Morgan WF | title = Radiation-induced genomic instability and its implications for radiation carcinogenesis | journal = Oncogene | volume = 22 | issue = 37 | pages = 5848–54 | date = September 2003 | pmid = 12947391 | doi = 10.1038/sj.onc.1206697 | doi-access = free }}</ref> causing chromosomal breakages and rearrangement of the chromosomes such as [[Chromosomal translocation|translocation]], [[Deletion (genetics)|deletion]], and [[Chromosomal inversion|inversion]]. Such mutagens are called [[clastogen]]s.

Mutagens may also modify the DNA sequence; the changes in [[nucleic acid]] sequences by mutations include substitution of [[nucleotide]] [[base-pair]]s and [[insertional mutation|insertions]] and [[deletion (genetics)|deletions]] of one or more nucleotides in DNA sequences. Although some of these mutations are lethal or cause serious disease, many have minor effects as they do not result in residue changes that have significant effect on the structure and function of the [[protein]]s. Many mutations are [[silent mutation]]s, causing no visible effects at all, either because they occur in non-coding or non-functional sequences, or they do not change the [[amino-acid]] sequence due to the [[redundancy (information theory)|redundancy]] of [[codon]]s.<ref>{{cite journal |last1=Durland |first1=Justin |last2=Ahmadian-Moghadam |first2=Hamid |date=19 September 2022 |title=Genetics, Mutagenesis |url=https://www.ncbi.nlm.nih.gov/books/NBK560519/ |journal=StatPearls |volume=2023 Jan |doi= |access-date=18 November 2023}}
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Some mutagens can cause [[aneuploidy]] and change the number of chromosomes in the cell. They are known as aneuploidogens.<ref>{{cite journal | vauthors = Duesberg P, Rasnick D | title = Aneuploidy, the somatic mutation that makes cancer a species of its own | journal = Cell Motility and the Cytoskeleton | volume = 47 | issue = 2 | pages = 81–107 | date = October 2000 | pmid = 11013390 | doi = 10.1002/1097-0169(200010)47:2<81::AID-CM1>3.0.CO;2-# }}</ref>

In Ames test, where the varying concentrations of the chemical are used in the test, the dose response curve obtained is nearly always linear, suggesting that there may be no threshold for mutagenesis. Similar results are also obtained in studies with radiations, indicating that there may be [[Linear no-threshold model|no safe threshold]] for mutagens. However, the no-threshold model is disputed with some arguing for a [[threshold model|dose rate dependent threshold]] for mutagenesis.<ref>{{Cite web|url=https://phys.org/news/2017-01-calabrese-lnt-toxicology.html|title=Calabrese says mistake led to adopting the LNT model in toxicology|date=2017|website=phys.org|archive-url=https://web.archive.org/web/20170801234403/https://phys.org/news/2017-01-calabrese-lnt-toxicology.html|archive-date=1 August 2017|url-status=live|access-date=24 Jan 2019|postscript=. Calabrese says mistake led to adopting the LNT model in toxicology.}}</ref><ref name="Calabrese Nobel lecture"/> Some have proposed that low level of some mutagens may stimulate the [[DNA repair]] processes and therefore may not necessarily be harmful. More recent approaches with sensitive analytical methods have shown that there may be non-linear or bilinear dose-responses for genotoxic effects, and that the activation of DNA repair pathways can prevent the occurrence of mutation arising from a low dose of mutagen.<ref>{{cite journal | vauthors = Klapacz J, Pottenger LH, Engelward BP, Heinen CD, Johnson GE, Clewell RA, Carmichael PL, Adeleye Y, Andersen ME | title = Contributions of DNA repair and damage response pathways to the non-linear genotoxic responses of alkylating agents | journal = Mutation Research/Reviews in Mutation Research | volume = 767 | pages = 77–91 | date = 2016 | pmid = 27036068 | pmc = 4818947 | doi = 10.1016/j.mrrev.2015.11.001 | bibcode = 2016MRRMR.767...77K | display-authors = 3 }}</ref>