Editing Centromere (section)

== Sequence ==
There are two types of centromeres.<ref>{{cite journal | vauthors = Pluta AF, Mackay AM, Ainsztein AM, Goldberg IG, Earnshaw WC | title = The centromere: hub of chromosomal activities | journal = Science | volume = 270 | issue = 5242 | pages = 1591–1594 | date = December 1995 | pmid = 7502067 | doi = 10.1126/science.270.5242.1591 | s2cid = 44632550 | bibcode = 1995Sci...270.1591P }}</ref> In regional centromeres, [[DNA]] sequences contribute to but do not define function. Regional centromeres contain large amounts of DNA and are often packaged into [[heterochromatin]]. In most [[eukaryotes]], the centromere's DNA sequence consists of large arrays of repetitive DNA (e.g. [[satellite DNA]]) where the sequence within individual repeat elements is similar but not identical. In humans, the primary centromeric repeat unit is called α-satellite (or alphoid), although a number of other sequence types are found in this region.<ref name="Mehta2010">{{cite journal | vauthors = Mehta GD, Agarwal MP, Ghosh SK | title = Centromere identity: a challenge to be faced | journal = Molecular Genetics and Genomics | volume = 284 | issue = 2 | pages = 75–94 | date = August 2010 | pmid = 20585957 | doi = 10.1007/s00438-010-0553-4 | s2cid = 24881938 }}</ref> Centromere satellites are hypothesized to evolve by a process called layered expansion. They evolve rapidly between species, and analyses in wild mice show that satellite copy number and heterogeneity relates to population origins and subspecies.<ref name="Arora et al">{{cite journal | vauthors = Arora UP, Charlebois C, Lawal RA, Dumont BL | title = Population and subspecies diversity at mouse centromere satellites | journal = BMC Genomics | volume = 22 | issue = 1 | pages = 279 | date = April 2021 | pmid = 33865332 | pmc = 8052823 | doi = 10.1186/s12864-021-07591-5 | doi-access = free }}</ref> Additionally, satellite sequences may be affected by inbreeding.<ref name="Arora et al" />

Point centromeres are smaller and more compact. DNA sequences are both necessary and sufficient to specify centromere identity and function in organisms with point centromeres. In budding yeasts, the centromere region is relatively small (about 125 bp DNA) and contains two highly conserved DNA sequences that serve as binding sites for essential [[kinetochore]] proteins.<ref name="Mehta2010"/>