Editing Repeated sequence (DNA) (section)

=== Huntington's disease ===
[[File:Huntington's_disease_(5880985560).jpg|thumb|280x280px|Image of the repeated DNA sequence in Huntington's disease.]]
[[Huntington's disease]] is a neurodegenerative disorder which is due to the expansion of repeated trinucleotide sequence CAG in [[exon]] 1 of the ''[[huntingtin]]'' gene (''HTT''). This gene is responsible for encoding the protein huntingtin which plays a role in preventing apoptosis,<ref>{{cite journal | vauthors = Cattaneo E, Zuccato C, Tartari M | title = Normal huntingtin function: an alternative approach to Huntington's disease | journal = Nature Reviews. Neuroscience | volume = 6 | issue = 12 | pages = 919–930 | date = December 2005 | pmid = 16288298 | doi = 10.1038/nrn1806 | s2cid = 10119487 }}</ref> otherwise known as cell death, and [[DNA repair|repair of oxidative DNA damage]].<ref>{{cite journal | vauthors = Maiuri T, Mocle AJ, Hung CL, Xia J, van Roon-Mom WM, Truant R | title = Huntingtin is a scaffolding protein in the ATM oxidative DNA damage response complex | journal = Human Molecular Genetics | volume = 26 | issue = 2 | pages = 395–406 | date = January 2017 | pmid = 28017939 | doi = 10.1093/hmg/ddw395 | doi-access = free }}</ref>  In Huntington's disease the expansion of the trinucleotide sequence CAG encodes for a mutant huntingtin protein with an expanded polyglutamine domain.<ref>{{cite journal | vauthors = Schulte J, Littleton JT | title = The biological function of the Huntingtin protein and its relevance to Huntington's Disease pathology | journal = Current Trends in Neurology | volume = 5 | pages = 65–78 | date = January 2011 | pmid = 22180703 | pmc = 3237673 }}</ref> This domain causes the protein to form aggregates in nerve cells preventing normal cellular function and resulting in neurodegeneration.
[[File:Fragile_X_Chromosomal_Differences.png|thumb|280x280px|Fragile X repeated CCG DNA sequence in comparison to a normal X chromosome.]]