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Editorials |
Departments of Neurology and Pediatrics, and the Center for the, Study of Neurodegenerative Disorders, University of Virginia School of Medicine, Charlottesville, VA 22901, E-mail dp8m@virginia.edu
Since the discovery that Leber hereditary optic neuropathy (LHON) results from mutations in mitochondrial DNA (mtDNA), considerable attention has been focused on this alternative genome and on development of the scientific tools needed to study this remarkable genetic pathway (1)(2). In this issue, Chen et al. (3) describe the application of temporal temperature gradient gel electrophoresis to the detection of mtDNA mutations and show that this technique offers great promise in this application.
The study of mitochondrial gene mutations presents investigators with
new technical problems not inherent to the study of nuclear gene
mutations. This genome is thought to be derived from an evolutionarily
ancient organism that parasitized primitive cells, conferring on them
enhanced oxidative capacity and the capability of making profitable use
of atmospheric oxygen, a fairly toxic substance. The structure of the
present day human mitochondrial genome reflects its unusual origin. The
mitochondrial genome is a small (16.5 kb) circular DNA encoding only 13
proteins, 2 rRNAs, and a set of tRNAs. All proteins encoded by the
mitochondrial genome are components of the mitochondrial electron
transport chain, the energy-transducing, oxidative apparatus of the
cell. Unlike nuclear genes, which exist in pairs by virtue of their
location on paired chromosomes, mitochondrial genes exist in numerous
copies per cell, with each mitochondrion containing several copies of
the genome and each cell containing many mitochondria. In the case of a
nuclear gene, only a limited number of combinations of mutated genes
are possible: a situation in which
References
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