Your cells need energy to function, and they make the most of the energy from mitochondria. Of course, researchers have been very interested in studying this cellular organelle, but we are still experiencing surprises. We have long thought that mitochondrial DNA has only gone down by the mothers. A team of researchers from the United States, China and Taiwan has identified several families where it is not true. They have a mixture of mitochondrial DNA from both mother and paternal lines, which is quite strange.
If you were noticed in high school biology, you probably learned that mitochondria are “the powerhouse of the cell” and not much else. Your cells use a molecule called ATP as an energy storage mechanism, and several metabolic processes in your body can produce it. Mitochondria pumps out most ATP, which makes them essential to your cells. Mitochondria has its own genomic separation from DNA in the nucleus of the cell that controls everything else about you. Mitochondria and their DNA should all come from your mother – they are from the original egg cell rather than the sperm. However, that is not the case for everyone.
Defects in mitochondria can lead to severe metabolic diseases, so doctors sometimes test mitochondrial DNA in patients. That was what doctors at the Cincinnati Children‘s Hospital Medical Center did for a four-year-old boy with a suspected mitochondrial disease. They found that his mitochondrial DNA had abnormally high heteroplasmic genes from different sources, both mother and father. Doctors tested the next boy’s family who were looking for the same deviation, found it in his mother, grandfather and two big aunt.
The Cincinnati team led by Taosheng Huang reached other locations around the world looking for other people with heteroplasm in their mitochondria. They found two more unrelated family lines with the same strange patterns of mitochondrial legacy. Children in these families seem likely to get a mixture of mitochondria in their perception, and mothers pass that mixture on their offspring. So, even a person without a “trigger” for this condition can still quit mixed mitochondria.
Researchers are currently uncertain of how modern mitochondria enter these cells; We only know that happens. A fertilized egg cell will eradicate some paternal mitochondria, but some people may carry a mutation that makes that mechanism less effective. Whatever the reason, it looks like a very rare occurrence. The authors say that the mother’s mitochondrial DNA is still “absolutely dominant”.
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