Editing Mitochondrial DNA (section)

=== Genetic illness ===
{{Further|Mitochondrial disease}}
Mutations of mitochondrial DNA can lead to a number of illnesses including [[exercise intolerance]] and [[Kearns–Sayre syndrome]] (KSS), which causes a person to lose full function of heart, eye, and muscle movements. Some evidence suggests that they might be major contributors to the aging process and [[Aging-associated diseases|age-associated pathologies]].<ref>{{Cite journal |vauthors=Alexeyev MF, Ledoux SP, Wilson GL |date=October 2004 |title=Mitochondrial DNA and aging |journal=Clinical Science |volume=107 |issue=4 |pages=355–364 |doi=10.1042/CS20040148 |pmid=15279618 |s2cid=5747202}}</ref> Particularly in the context of disease, the proportion of mutant mtDNA molecules in a cell is termed [[heteroplasmy]]. The within-cell and between-cell distributions of heteroplasmy dictate the onset and severity of disease<ref>{{Cite journal |vauthors=Burgstaller JP, Johnston IG, Poulton J |date=January 2015 |title=Mitochondrial DNA disease and developmental implications for reproductive strategies |journal=Molecular Human Reproduction |volume=21 |issue=1 |pages=11–22 |doi=10.1093/molehr/gau090 |pmc=4275042 |pmid=25425607}}</ref> and are influenced by complicated [[cellular noise|stochastic processes]] within the cell and during development.<ref name=pmid26035426/><ref>{{Cite journal |display-authors=6 |vauthors=Burgstaller JP, Johnston IG, Jones NS, Albrechtová J, Kolbe T, Vogl C, Futschik A, Mayrhofer C, Klein D, Sabitzer S, Blattner M, Gülly C, Poulton J, Rülicke T, Piálek J, Steinborn R, Brem G |date=June 2014 |title=MtDNA segregation in heteroplasmic tissues is common in vivo and modulated by haplotype differences and developmental stage |journal=Cell Reports |volume=7 |issue=6 |pages=2031–2041 |doi=10.1016/j.celrep.2014.05.020 |pmc=4570183 |pmid=24910436}}</ref>

Mutations in mitochondrial tRNAs can be responsible for severe diseases like the [[MELAS syndrome|MELAS]] and [[MERRF syndrome|MERRF]] syndromes.<ref name="nature">{{Cite journal |vauthors=Taylor RW, Turnbull DM |date=May 2005 |title=Mitochondrial DNA mutations in human disease |journal=Nature Reviews. Genetics |volume=6 |issue=5 |pages=389–402 |doi=10.1038/nrg1606 |pmc=1762815 |pmid=15861210}}</ref>

Mutations in nuclear genes that encode proteins that mitochondria use can also contribute to mitochondrial diseases. These diseases do not follow mitochondrial inheritance patterns but instead follow Mendelian inheritance patterns.<ref>{{Cite journal |vauthors=Angelini C, Bello L, Spinazzi M, Ferrati C |date=July 2009 |title=Mitochondrial disorders of the nuclear genome |journal=Acta Myologica |volume=28 |issue=1 |pages=16–23 |pmc=2859630 |pmid=19772191}}</ref>