Editing Microsatellite (section)

==Structures, locations, and functions==
A microsatellite is a tract of tandemly repeated (i.e. adjacent) DNA motifs that range in length from one to six or up to ten nucleotides (the exact definition and delineation to the longer minisatellites varies from author to author),<ref name="Richard 2008"/><ref name="Gulcher2012"/> and are typically repeated 5–50 times. For example, the sequence TATATATATA is a dinucleotide microsatellite, and GTCGTCGTCGTCGTC is a trinucleotide microsatellite (with A being [[Adenine]], G [[Guanine]], C [[Cytosine]], and T [[Thymine]]). Repeat units of four and five nucleotides are referred to as tetra- and pentanucleotide motifs, respectively. Most [[eukaryote]]s have microsatellites, with the notable exception of some yeast species. Microsatellites are distributed throughout the genome.<ref name="King 1997">{{cite journal | vauthors = King DG, Soller M, Kashi Y |year=1997 |title=Evolutionary tuning knobs  | journal=Endeavour |volume=21 |issue=1 |pages=36–40 |doi=10.1016/S0160-9327(97)01005-3}}</ref><ref name="Richard 2008">{{cite journal | author1 = Richard GF | author2 = Kerrest A | author3 = Dujon B | author-link3 = Bernard Dujon| title = Comparative genomics and molecular dynamics of DNA repeats in eukaryotes | journal = Microbiology and Molecular Biology Reviews | volume = 72 | issue = 4 | pages = 686–727 | date = December 2008 | pmid = 19052325 | pmc = 2593564 | doi = 10.1128/MMBR.00011-08 }}</ref><ref>{{Cite journal| vauthors = Chistiakov DA, Hellemans B, Volckaert FA |date=2006-05-31|title=Microsatellites and their genomic distribution, evolution, function and applications: A review with special reference to fish genetics | journal=Aquaculture|volume=255|issue=1–4|pages=1–29|doi=10.1016/j.aquaculture.2005.11.031|bibcode=2006Aquac.255....1C }}</ref> The human genome for example contains 50,000–100,000 dinucleotide microsatellites, and lesser numbers of tri-, tetra- and pentanucleotide microsatellites.<ref name="Turnpenny 2005">{{cite book | vauthors = Turnpenny P, Ellard S |date=2005 |title=Emery's Elements of Medical Genetics |url=https://archive.org/details/emeryselementsof0000turn_12ed |url-access=registration |edition=12th |location=London |publisher=Elsevier|isbn=9780443100451 }}</ref> Many are located in non-coding parts of the human genome and therefore do not produce proteins, but they can also be located in regulatory regions and [[coding region]]s.

Microsatellites in non-coding regions may not have any specific function, and therefore might not be [[Natural selection|selected]] against; this allows them to accumulate mutations unhindered over the generations and gives rise to variability that can be used for DNA fingerprinting and identification purposes. Other microsatellites are located in regulatory flanking or [[intronic]] regions of genes, or directly in [[codon]]s of genes&nbsp;– microsatellite mutations in such cases can lead to phenotypic changes and diseases, notably in [[Trinucleotide repeat disorder|triplet expansion diseases]] such as [[fragile X syndrome]] and [[Huntington's disease]].<ref name="Pearson 2005"/>

[[Telomeres]] are linear sequences of DNA that sit at the very ends of chromosomes and protect the integrity of genomic material (not unlike an [[aglet]] on the end of a shoelace) during successive rounds of cell division due to the "end replication problem".<ref name="Gulcher2012" /> In white blood cells, the gradual shortening of telomeric DNA has been shown to inversely correlate with [[ageing]] in several sample types.<ref>{{cite journal | vauthors = Goldman EA, Eick GN, Compton D, Kowal P, Snodgrass JJ, Eisenberg DT, Sterner KN | title = Evaluating minimally invasive sample collection methods for telomere length measurement | journal = American Journal of Human Biology | volume = 30 | issue = 1 | pages = e23062 | date = January 2018 | pmid = 28949426 | pmc = 5785450 | doi = 10.1002/ajhb.23062 }}</ref> Telomeres consist of repetitive DNA, with the hexanucleotide repeat motif TTAGGG in vertebrates.{{Citation needed|date=June 2022}} They are thus classified as [[minisatellite]]s. Similarly, insects have shorter repeat motifs in their telomeres that could arguably be considered microsatellites.{{Citation needed|date=June 2022}}