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A piece of high school genetics, used for many types of genetic testing, presents exceptions. Although mitochondrial DNA (mtDNA) is normally received from the mother, three families have been identified and some have received part of their mtDNA, three-quarters in the most extreme case, from their father. The discovery could change the way we treat mitochondrial diseases and challenge genetic testing for maternal ancestry.
The mADn exists separately from the rest of our DNA, inside thousands of mitochondria in each cell, rather than in the nucleus of the cell. It is so widely accepted as being on the mother's side that it is sometimes called the Eve gene, the idea being that it can be traced back to a primitive mother of all living human beings. The mtDNA test is used to identify maternal ancestry.
However, all of this will have to change after Dr. Shiyu Luo of the Cincinnati Children's Hospital Medical Center published an article in the Proceedings of the National Academy of Sciences.
Luo's first exception concerns a boy who, at age four, was hospitalized with symptoms suggestive of mitochondrial disease. Sequencing of the boy's mitochondria revealed no pathogenic genes, but some abnormalities in the mDNA that led Luo and his colleagues to sequence other family members for comparison purposes. About 40% of the boy's mitochondria corresponded to that of his mother's father and only 60% of his grandmother.
After testing other members of the same family and other families with mitochondrial diseases, Luo found that, although the paternal inheritance is very rare, it occurred at least 17 times in three families tested.
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