The finding zeroes in on the components of cells called the mitochondria, the main sources of the body’s energy. These tiny bean-shaped constituents, found in each cell, carry their own DNA, apart from the body’s nuclear genes inherited from both parents. Mitochondrial DNA has been believed passed from one generation to the next only along a maternal line of inheritance. Fathers, scientists long believed, did not transmit them. The sperm cell’s few mitochondria, scientists discovered only two years ago, are assassinated by killer proteins in the egg. This molecular murder plot is carried out not long after conception.
Now, Dr. Marianne Schwartz and colleagues in the department of clinical genetics at the Copenhagen Muscle Research Centre have found that a man not only has inherited paternal mitochondria, but he has developed a genetic muscle disease caused by a distinct defect due to paternal inheritance.
This discovery, repeatedly tested for accuracy, adds to the many mysteries of mitochondria. Scientists postulate that mitochondria are relic of distant primordial origin, possibly existing once as bacteria that insinuated themselves into mammalian cells. They have been with all mammals every since, producing the energy forever conceivable activity.
Scientist at Emory University discovered the first mitochondria disease only in 1988, a fatal genetic disorder characterised blindness and muscle wasting that is passed from mothers to sons.
Schwartz describes the Danish man’s disorder as a lifelong inability to perform exercise. Though it is not fatal, it is debilitating. The patient had never been able to run more than a few steps before reaching exhaustion. Both parents and a sister were free of such problems.
A microscopic examination of the penitent’s tissues revealed the telltale signs of a mitochondria disease. Muscle fibers appeared red and ragged. Even more shocking, two types of mitochondria were in the man’s cells, evidence that both parents had contributed the constituents at conception. Mitochondria from the patient’s father had not been destroyed after all.
Dr. L. Sanders Williams of Duck University said Schwartz and her team were able to determine the patient bore defective mitochondria from his father because they were able to sample mitochondria DNA from both of the patient’s parents.
Elsas says the finding could lead to the discovery of other paternally inherited mitochondria diseases. The finding also has implications for evolutionary sciences, exploding the possibility that humans can be traced over many millennia through mitrochondrial DNA. Geneticist Douglas Wallace, then of Emory University, created a stir in the 1980s when he postulated that all modern humans were derived from a woman in Africa whose descendants populated the Earth. He made the claim based on mitochondrial DNA. It will be more difficult to make such claims if mitrochondrial DNA can be inherited from both parents, not just the mother.