Editing Tandem repeat (section)

{{short description|Adjacent repeated pattern of nucleotides within DNA}}
{{Distinguish|Tandemly arrayed genes}}

In [[genetics]], '''tandem repeats''' occur in [[DNA]] when a pattern of one or more [[nucleotide]]s is repeated and the repetitions are directly adjacent to each other, e.g. ATTCG ATTCG ATTCG, in which the sequence ATTCG is repeated three times.<ref>{{MeshName|Tandem+Repeat}}</ref>

Several [[protein domain]]s also form [[Protein tandem repeats|tandem repeats]] within their amino acid [[primary structure]], such as [[armadillo repeat]]s. However, in proteins, perfect tandem repeats are rare in naturally proteins, but they have been added to designed proteins.<ref>{{cite journal |vauthors=Jorda J, Xue B, Uversky VN, Kajava AV |title=Protein tandem repeats - the more perfect, the less structured |journal=The FEBS Journal |volume=277 |issue=12 |pages=2673–82 | date=June 2010 |pmid=20553501 |pmc=2928880 |doi=10.1111/j.1742-4658.2010.07684.x}}</ref>

Tandem repeats constitute about 8% of the [[human genome]].<ref>{{cite journal | vauthors = Duitama J, Zablotskaya A, Gemayel R, Jansen A, Belet S, Vermeesch JR, Verstrepen KJ, Froyen G | title = Large-scale analysis of tandem repeat variability in the human genome | journal = Nucleic Acids Research | volume = 42 | issue = 9 | pages = 5728–5741 | date = May 2014 | pmid = 24682812 | pmc = 4027155 | doi = 10.1093/nar/gku212 }}</ref> They are implicated in more than 50 lethal human [[disease]]s, including [[ALS|amyotrophic lateral sclerosis]], [[Huntington's disease]], and several [[cancer]]s.<ref>{{Cite journal |last1=Cui |first1=Ya |last2=Ye |first2=Wenbin |last3=Li |first3=Jason Sheng |last4=Li |first4=Jingyi Jessica |last5=Vilain |first5=Eric |last6=Sallam |first6=Tamer |last7=Li |first7=Wei |date=April 2024 |title=A genome-wide spectrum of tandem repeat expansions in 338,963 humans |journal=Cell |volume=187 |issue=9 |pages=2336–2341.e5 |doi=10.1016/j.cell.2024.03.004 |issn=0092-8674|doi-access=free |pmid=38582080 |pmc=11065452 }}</ref>