“Mitochondria may not be inherited solely through the maternal line”, reported New Scientist (23 August 2002). The discovery stands to overturn decades of “accepted biological wisdom” and “could have huge implications for evolutionary biology and biochemistry”.

Until now, paternal mitochondria were thought to be destroyed during conception, leaving only maternal mitochondria to be inherited. But, when sequencing the mitochondrial DNA from a 28-year-old patient, Marianne Schwartz and John Vissing from the University Hospital Rigshospitalet in Copenhagen unexpectedly found that a large percentage of his mitochondria came from his father.

These findings, published in the New England Journal of Medicine, outline the first case of paternal mitochondrial inheritance. The patient, who suffers from extreme fatigue during exercise, appeared to be clinically healthy. But, Schwartz and Vissing identified two mutations in his mitochondrial DNA which were found to map to his father and not, as expected, to his mother. “Muscle biopsies showed that about 90 per cent of his mitochondria came from his father. However, the mitochondria in his blood, hair roots and fibroblasts came entirely from his mother”(New Scientist).

The researchers believe that paternal inheritance of mitochondria will probably remain a rare event. It is clear that these findings need to be confirmed, but for many evolutionary biologists, and for those scientists interested in metabolic diseases, these surprising results will force a re-evaluation of ideas.