The structures produce energy found in & # 39; of each of our cells usually only inherited from his mother. But doctors in the United States now have identified more than a dozen people in three different families mitochondria inherited from both parents.
It seems that these individuals are very rare exceptions to the usual rule, x & # 39; likely because these families have mutations that disrupt the mechanism that normally prevents the mitochondria & # 39; father passed his children.
The mitochondria produce the cells & # 39; energy needs to function and every human cell, including sperm and eggs, which many of them. But although the mitochondria & # 39; father enters the egg, in humans a chemical tag that marks them for destruction, so generally all mitochondria come from the mother.
However, in 2002 it was found that cells of & # 39; one man had a mixture of & # 39; mitochondria from his father and his mother. But no other cases have been reported, some questioned whether the statement of 2002 was correct.
Now a team at Medical Center of Children's Hospital & # 39; Cincinnati in the United States say they have "unequivocal" evidence having identified 17 such people with such paternal inheritance.
More and more cases
The first person was targeted because he was suffering from fatigue and muscle pain, which was suspected to have been caused by mitochondrial mutations. It turns out that wireta mitochondria from both parents, and emerged a new mutation in the paternal mitochondria.
During their investigation, the team found that other family members also mix & # 39; maternal and paternal mitochondria in & # 39; of each of their cells. Then studied other patients & # 39; & # 39 symptoms, mitochondrial diseases, and found two other families as well.
"The surprise is that we really do not see more than that," says Nick Lane at University College London in the United Kingdom, author & # 39; book on mitochondria. His team predicted the last year that "father leakage" should be relatively common in all organisms with & # 39; mitochondria.
Why? Because there are two conflicting evolutionary forces at work. In a short time, mixing mitochondria can & # 39; & # 39 has; benefit to individuals because the father mitochondria, say, you & # 39; offset mutation & # 39; damage the mother's mitochondria. But long-& # 39; time, it can & # 39; reduce capacity & # 39; evolution to eliminate harmful mutations that are hidden from view.
Lane thinks that this is the reason why organisms have a wide variety & # 39; mechanisms to ensure that the mitochondria is inherited only from the mother. Over the course of & # 39; evolution, species have developed such mechanisms repeatedly, tilfuhom and then evolved similar mechanisms other again & # 39;, his team proposed.
Since mitochondrial DNA is the most common type of & # 39; DNA into cells – since each cell can & # 39; contains hundreds & # 39; copies – has been widely used in genetic studies, for example to study our evolutionary history. If the paternal inheritance of mitochondria was very common it weakens some of the conclusions of & # 39; these studies, but x & # 39; likely still so rare that makes little difference.
the Journal reference: PNAS, DOI: 10.1073 / pnas.1810946115
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