Abstract
Mitochondria are unique among cellular organelles in that they contain their own genetic material—about 2 to 10 copies of a double-stranded, circular DNA molecule that is approximately 16.5 kilobases (kb) in length. This is very small as compared, for example, with the dystrophin gene (2000 kb), which is abnormal in Duchenne's and Becker's muscular dystrophies.Mitochondrial DNA differs from the DNA in the cell nucleus in three important respects: it is transmitted exclusively by mothers, it contains few noncoding sequences (introns), and it has a slightly different genetic code; for example, the uridine–guanine–adenine (UGA) codon is read as "tryptophan" rather . . .