If confirmed by other researchers, the findings could have huge implications for evolutionary biology and biochemistry.
Robert Sanders Williams, from Duke University Medical Center in North Carolina, says the findings are 'remarkable and unanticipated. This is more than a mere curiosity. It asserts the principle that it can occur in humans. It could have significant implications for the study of human evolution and the migrations of populations,' he says.
For decades biologists have assumed that mitochondria - the cells' power stations - are inherited solely through the maternal line.
Mitochondria in the sperm from the father were presumed to be destroyed immediately after conception, leaving behind only those from the mother. But Marianne Schwartz and John Vissing from the University Hospital Rigshospitalet in Copenhagen, have discovered that one of their patients inherited the majority of his mitochondria from his father.
Even with very sensitive methods, paternal mitochondrial DNA has never been detected in man before, Schwartz told Reuters. There are many examples of family pedigrees that follow mitochondrial diseases through the maternal line.
The pair made the discovery while trying to discover why one of their patients suffered extreme fatigue during exercise. The 28-year-old man had an entirely normal heart and lungs and his muscles appeared healthy. But on closer inspection, Schwartz and Vissing discovered that his muscles absorbed very little oxygen.
This led them to examine the genetic sequence of his mitochondria. They discovered two mutations in his mitochondrial DNA one of which was responsible for his extreme fatigue.
To try and investigate the mutations further, they also sequenced the DNA of his mother, father and uncle. To their surprise, the sequence matched those of his father and uncle.
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.
The two mutations appear to have arisen spontaneously during, or shortly after, conception.
The researchers think inheritance of paternal mitochondrial DNA is probably very rare. But the findings will have implications for a number of branches of biology. Evolutionary biologists often date the divergence of species by the differences in genetic sequences in mitochondrial DNA. Even if paternal DNA is inherited very rarely, it could invalidate many of their findings. It will also have implications for scientists investigating inherited metabolic diseases.
Journal reference: New England Journal of Medicine (vol 347, p576)
23 August 2002