New insight into DNA
By Nancy Battick
For years we’ve been told that MtDNA (maternal DNA) is passed from mother to children, both male and female, but only daughters pass it on to their own children. Now research has revealed that in rare instances this is not the case.
A 2018 article in the Proceedings of the National Academy of Science (visit the website at www.pnas.org) details a study that revealed several occurrences where some of the MtDNA of the father also was inherited by the children. Studies of other family relatives revealed that they, too, passed on some of their MtDNA to their offspring. In addition, other cases were identified.
This is stunning. For years experts have taught us that MtDNA is the gift of the mother, just as Y-DNA is exclusive to the father.
While Paternal MtDNA has been known to pass to offspring in plants, insects and some animals, these are the first scientifically proven cases in humans. What it means that through a process termed “paternal leakage,” some of Dad’s MtDNA inherited from his mother was able to move to the next generation. Normally, this doesn’t happen because the mother’s MtDNA is genetically programmed to destroy all of Dad’s. Now we know this isn’t always the case.
The article emphasizes that this is extremely rare, at least to date. I suspect that it is so rare that it’s flown under the radar for some time, but there’s no telling how many other humans may carry some of their father’s ancestral MtDNA. And also, MtDNA tests aren’t able to differentiate paternal from maternal DNA. This means the results of MtDNA tests may contain paternal MtDNA, but without recognizing it as such.
I searched online, not only at the Proceedings of the National Academy of Science website, where you can read the original article, but I found at least a couple of dozen articles on this. They ranged from the National Institute of Health, Nature, the World Mitochondria Society to Wikipedia. You can find these by using your search engine. The articles can be technical, but if you’re interested in DNA, you can make your way through them.
What all this emphasizes is that studies on DNA are ongoing, which is what science is all about. Often people complain that scientists keep changing their stories, but that’s to be expected and is perfectly normal as new tests, data and situations arise. Science is always in flux, as this discovery reveals. I have a feeling more discoveries will emerge as time goes by.
I don’t know where these studies will take us. I freely admit I’m not an expert on DNA and wouldn’t presume doing much more than marvel at this. These results prove that DNA is more complicated than believed, and that the future will reveal more surprises.
As genealogists, we often rely on DNA tests to aid us in researching family and origins. These types of discoveries can shake our preconceived notions about what DNA can reveal.
On an unrelated note, I wish each of you happy holidays.
Columnist Nancy Battick of Dover-Foxcroft has researched genealogy for over 30 years. She is past president of the Maine Genealogical Society, author of several genealogical articles and co-transcribed the Vital Records of Dover-Foxcroft. Nancy holds an MA in History from UM. Reader emails are welcome at nbattick@roadrunner.com.