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December 2013

Mitochondrial DNA Mutation LoadChance or Destiny?

Author Affiliations
  • 1Department of Neurology, Columbia University Medical Center, New York, New York
JAMA Neurol. 2013;70(12):1484-1485. doi:10.1001/jamaneurol.2013.4401

It is well known that mitochondrial DNA (mtDNA)–related disorders are clinically heterogeneous, even within the same family.1 This is because in most patients, pathogenic mtDNA mutations are heteroplasmic, that is, a mixture of normal and mutated mtDNAs. Moreover, applying Mendelian terminology to mitochondrial genetics, heteroplasmic mtDNA mutations are recessive in the sense that very high proportions of a mutation are needed before a clinical phenotype becomes manifest. This threshold effect varies among mutation types and is generally higher for transfer RNA (tRNA) mutations than for protein-coding gene mutations or large-scale single deletions.

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