For those who do not work on mitochondria, their knowledge is often restricted to eubacterial origins, production of ATP and perhaps an appreciation of the non-Mendelian maternal inheritance patterns. These features are true enough, but things then start to get more complicated. Although the origins of mitochondria are accepted as a eubacterial endosymbiont of evolving eukaryotic cells1, there were organisms that were described as having jettisoned these ‘organelles’, referred to as amitochondriate eukaryotes. This concept has been challenged, and rudimentary mitochondria, or mitosomes, have now been found in those eukaryotes, which are apparently reluctant to lose this organelle2. The consequences of mitochondrial evolution can be seen in the divergence from the standard repertoire of RNA elements. These eccentricities pose challenges to our understanding of molecular mechanisms underlying mitochondrial gene expression.

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