Editing Mutagenesis (section)

=== Dimerization ===
{{Main|Dimer (chemistry)|l1=Dimer}}

Dimerization consists of the bonding of two monomers to form an oligomer, such as the formation of [[pyrimidine dimer]]s as a result of exposure to [[Ultraviolet|UV radiation]], which promotes the formation of a cyclobutyl ring between adjacent thymines in DNA.<ref>{{Cite journal|last1=Setlow|first1=R. B.|year=1966|title=Cyclobutane-type pyrimidine dimers in polynucleotides|journal=Science|volume=153|issue=734|pages=379–386|bibcode=1966Sci...153..379S|doi=10.1126/science.153.3734.379|pmid=5328566|s2cid=11210761}}</ref> In human skin cells, thousands of dimers may be formed in a day due to normal exposure to sunlight. [[DNA polymerase eta|DNA polymerase η]] may help bypass these lesions in an error-free manner;<ref>{{Cite journal|last1=Broyde|first1=S.|last2=Patel|first2=D. J.|year=2010|title=DNA repair: How to accurately bypass damage|journal=Nature|volume=465|issue=7301|pages=1023–1024|bibcode=2010Natur.465.1023B|doi=10.1038/4651023a|pmc=4986998|pmid=20577203}}</ref> however, individuals with defective DNA repair function, such as those with [[xeroderma pigmentosum]], are sensitive to sunlight and may be prone to skin cancer. [[Image:DNA intercalation2.jpg|thumb|left|250px|Ethidium intercalated between two adenine-thymine base pairs]] Clinically, whether a tumor has formed as a direct consequence of UV radiation is discernible via DNA sequencing analysis for the characteristic context-specific dimerization pattern that occurs due to excessive exposure to sunlight.<ref>{{cite journal |last1=Mata |first1=Douglas A. |last2=Williams |first2=Erik A. |last3=Sokol |first3=Ethan |last4=Oxnard |first4=Geoffrey R. |last5=Fleischmann |first5=Zoe |last6=Tse |first6=Julie Y. |last7=Decker |first7=Brennan |title=Prevalence of UV Mutational Signatures Among Cutaneous Primary Tumors |journal=JAMA Network Open |date=23 March 2022 |volume=5 |issue=3 |pages=e223833 |doi=10.1001/jamanetworkopen.2022.3833| pmid=35319765 |pmc=8943639 }}</ref>