Editing Repeated sequence (DNA) (section)

=== Fragile X syndrome ===
[[Fragile X syndrome]] is caused by the expansion of the DNA sequence CCG in the ''FMR1'' gene on the X chromosome.<ref>{{cite journal | vauthors = Penagarikano O, Mulle JG, Warren ST | title = The pathophysiology of fragile x syndrome | journal = Annual Review of Genomics and Human Genetics | volume = 8 | issue = 1 | pages = 109–129 | date = 2007-09-01 | pmid = 17477822 | doi = 10.1146/annurev.genom.8.080706.092249 }}</ref> This gene produces the RNA-binding protein FMRP. In the case of Fragile X syndrome the repeated sequence makes the gene unstable and therefore silences the gene ''FMR1.''<ref>{{cite journal | vauthors = Hagerman RJ, Berry-Kravis E, Hazlett HC, Bailey DB, Moine H, Kooy RF, Tassone F, Gantois I, Sonenberg N, Mandel JL, Hagerman PJ | display-authors = 6 | title = Fragile X syndrome | journal = Nature Reviews. Disease Primers | volume = 3 | issue = 1 | pages = 17065 | date = September 2017 | pmid = 28960184 | doi = 10.1038/nrdp.2017.65 | s2cid = 583204 }}</ref> Because the gene resides on the X chromosome, females who have two X chromosomes are less effected than males who only have on X chromosome and one Y chromosome because the second X chromosome can compensate for the silencing of the gene on the other X chromosome.