Hello Cousins,
I hope the Holidays are bright and safe for you all.
Recently an article (see below) claims paternal transmission of
mitochondrial DNA (mtDNA) implying that mtDNA tests can not be relied on for
maternal DNA studies. In total there is about 50 or so people documented
with this out of the 7.7 billion people in the world. Even the most
optimistic studies indicate a less than a tenth of one percent probability.
General rule of thumb - mtDNA is passed from the mother to her children, but
only the daughters can pass it to the next generation.
On the very very rare exceptions are when the maternal mtDNA is damaged in
some way and allows paternal mtDNA transmission to replace, or partially
replace the maternal mtDNA during recombination.
See the Smithsonian Magazine article dated 3 Dec 2018 and entitled "Dads
Also Pass on Mitochondrial DNA, Contrary to Long-Standing Belief - A new
study, which found paternal mitochondrial DNA in 17 individuals, upends the
commonly accepted theory that mtDNA comes exclusively from the mother"
Read more at:
https://www.smithsonianmag.com/smart-news/dads-also-pass-mitochondrial-dn...
Careful reading indicates the following line within the article.
"A remarkable study published recently in PNAS, however, suggests that
paternal mtDNA can coexist with maternal mtDNA on rare occasions."
Then there are these lines ...
"But the new study seems to settle a long-standing debate over whether it
was even possible for paternal and maternal mtDNA to coexist in humans. The
phenomenon has been documented in plants and a small number of animals, but
prior to the recent study, biparental mtDNA in humans had only been attested
to in a 2002 report, which described a single man who was found to have
mtDNA from both his mother and father in his skeletal muscle cells."
Who ever wrote this article seems to ignore human studies published in 1996,
1997, 1999 and else where which basically indicates the same thing prior to
the 2002 article. And they fail to state that this is not ground breaking
news, but it is a follow up of earlier research and study expansion going
back for about two decades.
It has been proven that paternal mtDNA transmission the X chromosome
transmitted by the male sperm can, on very rare occasions, be used to fix,
replace or interfere with the maternal mtDNA in the egg during
recombination. In addition, it is a strong suspect in extra or damaged
chromosomal abnormalities causing miscarriages, XXX and XXY type syndromes
and similar issues. And it is also a suspect in some vanishing twin syndrome
cases which can lead to absorption.
For those unfamiliar with vanishing twin syndrome, it is simply where 1) the
mother absorbs one twin usually within the first trimester or 2) one twin in
vitro absorbs the other twin leading to multiple types of DNA in the body.
Sometimes 3) there is a partial absorption or cells that often become
non-viable or if viable need corrective surgery.
For 2), this is often not discovered until some medical issue or other
abnormality is found and genetic testing is done. It is possible to have
both Y-DNA and mtDNA in one body or even two sets of mtDNA or other
combinations in one body. Again, this is very rare.
Now that science is more aware, they are finding supporting cases and
searching for more understanding of the whys this happens on occasion.
Please remember that Chimera and Mosiac events occur after recombination.
Suggested study links include...
Paternal mtDNA transmission -
https://www.nejm.org/doi/full/10.1056/nejmoa020350 (2002) - See Reference 27
for the 1997 research. See Letters then Response - "The authors reply"
which
cites two References regarding the 1996 and 1999 articles.
See the related ...
https://www.newscientist.com/article/dn2716-mitochondria-can-be-inherited...
(2002)
See also:
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(99)03842-...
(2000)
Genetic Chimera -
https://en.wikipedia.org/wiki/Chimera_(genetics) - See
also the stories at:
https://pictorial.jezebel.com/one-person-two-sets-of-dna-the-strange-case...
and
https://en.wikipedia.org/wiki/Lydia_Fairchild
Genetic mosaicism -
https://en.wikipedia.org/wiki/Mosaic_(genetics)
Parasitic twin -
https://en.wikipedia.org/wiki/Parasitic_twin
I hope this is educational and interesting.
John R. Carpenter
La Mesa, CA USA
Carpenter Cousins Project - Our main support page!
https://carpentercousins.com