You Can Inherit Mitochondrial DNA from Both Parents! | SciShow News
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You Can Inherit Mitochondrial DNA from Both Parents! | SciShow News


♪ Everybody knows that the DNA you inherit from
each biological parent is an even split… I mean, hopefully everybody knows: you get
half from the egg and half from the sperm that combines to make you. Well, almost. 37 genes are found in your mitochondria, those
little energy factories of cells. And that mitochondrial DNA only comes from
the egg. At least, that’s what we thought. Earlier this week, an international team of
researchers announced that they’d found strong evidence that mitochondrial DNA can
be inherited from both parents. Which could change what we know about not
only disease inheritance, but like… human history as a whole. It all started with a 4-year-old boy that
doctors suspected of having a mitochondrial disorder —a disease caused by mutations in
mitochondrial DNA. They’re tricker to diagnose and treat than
other genetic diseases because every cell in the body has several hundred mitochondria, and not all of them have the same DNA. Because mitochondrial disorders are complicated
and don’t always show up in tissue samples or fluid tests, the only way to diagnose one
with absolute certainty is with DNA sequencing. And when they sequenced this boy’s mitochondrial
DNA, they found a peculiar pattern of mutant genes. His mother and sisters had the same pattern,
which is exactly what you’d expect, and since none of them have a mitochondrial disorder,
the mutations don’t seem to explain his condition. But the pattern just stood out so much that
the team decided to test the boy’s grandparents, too. That was when they made a discovery that was
previously thought to be impossible: only some of his mother’s mutation pattern matched
her mother’s. The rest clearly matched up to the boy’s
grandfather. Even stranger, when they tested the grandfather’s
female relatives, they discovered that his pattern of mitochondrial mutations could also
be traced to both of his parents. To confirm their findings, the researchers
recruited two other, unrelated families with suspected mitochondrial disorders, and had
their mitochondrial DNA sequenced. And astonishingly, they found similar patterns. Some family members had inherited mitochondrial
variants from just their mothers, and some had inherited them from both parents. This isn’t the first study to suggest bi-parental
inheritance of mitochondria. Back in 2002, Danish researchers published
a report of a man with a mitochondrial disorder he appeared to have inherited from his father. Their results were independently verified
by Harvard researchers, who also uncovered potential evidence that mitochondrial DNA
could recombine, or mix just like regular DNA. But in the past decade and a half, no other
cases have been reported despite quite a bit of effort to find them. So the whole idea of bi-parental mitochondrial
inheritance — and especially questions of recombination — has remained a contentious
topic in genetics circles. This time, though, the researchers made absolutely
certain that their results were correct: they looked at dozens of people in three multi-generation
families, used incredibly sensitive testing methods, and had new DNA samples re-sequenced
at two other labs, just to be sure. And they wouldn’t have found any of this
if they’d stopped looking once they sequenced the boy’s mom and sisters, which is what many doctors would have done
since the mutations were inherited as expected and don’t appear to be the cause of his
ailment. If the idea that people can sometimes inherit
mitochondria from both parents doesn’t seem like a big deal, consider that mitochondrial DNA is one of
the best ways we have to trace the history of our species over centuries. Since it doesn’t change much from generation
to generation, the small changes that do show up in isolated groups —like populations of people living on different
continents— can be used to track where people came from
and how they moved around. And the changes are thought to happen at a
somewhat reliable rate, allowing us to estimate how long ago groups of people split from others. But all the math involved assumes that mitochondrial
DNA comes only from the egg—which, it seems, isn’t always the case. In fact, based on the findings, the authors
of the paper suspect babies might get some mitochondria from sperm as often as one in
every 5,000 births. And if that’s true — or if it turns out
that mitochondrial DNA can recombine, as those Harvard researchers suggested — then all
bets are off. The study authors, for their part, don’t
think their findings completely change things— there isn’t enough evidence, yet, to overturn
decades of research into human origins. But it’s early in the discovery process,
and it could be years before we really understand how all this messes with ancestry analyses
or our understanding of human history. More immediately, this study will likely affect
how doctors approach the genetic component to treating mitochondrial disorders, especially
since the team has a hypothesis for how this bizarre inheritance happened. At first, both parents contribute mitochondrial
DNA to a developing fetus, but when the egg is fertilized, a mitochondrial-killing mechanism
makes sure any mitochondria from the sperm get wiped from the slate. The researchers think that there might be
a mutation in a nuclear gene — that is, a gene somewhere in the main
set of chromosomes we think of as a person’s genome — that’s stopping that key step in development. If such a mutation exists, it could be passed
down through a family, leading to the mitochondrial DNA pattern they saw. The researchers are hoping further studies
will reveal exactly how the mitochondrial DNA from sperm survives. Knowing that will help us understand how commonly
it happens, and it may help us figure out how to stop it from happening— perhaps preventing
some mitochondrial disorders. It could even reveal a way to prevent disease-causing
mitochondria from the egg from being passed on. But all of that is speculation at this point. Until those future studies are done, we won’t
know whether the new findings will change our understanding of the history of humanity. But either way, they’re definitely teaching
us something new about our cells. Thanks for watching this episode of SciShow
News! And speaking of news, you might have noticed
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goodies, you can just click on that little “join” button
below the video. ♪

100 thoughts on “You Can Inherit Mitochondrial DNA from Both Parents! | SciShow News

  1. hmmm… Is it possible for for identical twins to have two different fathers? And if so, then is it also possible for fertilized egg to have mitochondrial DNA from a 3rd party? Someone call Jerry Springer!

  2. One of my best friends is a researcher who works with mitochondria, using CRSPR to knock out genes and find out what each protein does. She had not heard this news yet until I showed the video, even though it could definitely be relevant to her research.

  3. The difference between science and religion… science changes and accepts when it’s wrong. Religion is adamant on the acceptance of their stubborn beliefs and words carved into stone

  4. The cytoplasm in everyone's cells only comes their mother's egg. So, mitochondria isn't the only thing to be inherited solely from the mother.

  5. So what I understood from this is that they discovered evidence in three separate families, each with suspected or confirmed mitochondrial disorders, that some mitochondrial DNA came from paternal lineage and not just maternal. It is also theorized that, during ovum fertilization, mitochondrial DNA carried by the sperm cell is usually wiped away, so the previous observation may be due to the "wipe the slate" step being skipped.
    Given all this, theory: is it possible that certain mitochondrial disorders occur BECAUSE the "wipe the slate" step gets skipped? Think about it; the addition, deletion, or alteration of genes is well-known for causing a whole variety of conditions, so isn't it at least conceivable that an error during fertilization which directly affects the fetus' DNA could cause such disorders?

  6. So, the mother has a defect that did not prevent the father's mDNA from being excluded OR his mDNA has found a way to avoid that. Will an excess number of mitochondria give the offspring "superpowers" or just increase their cancer risk?

  7. yeah this explains why incest is really bad. Not that we really know the mechanism for action that causes problems in those cases. But the similarities seem to be a part of it. It's weird because there was Lot and we don't know much about why that happens it could be a subject for IVF-> Stem cell research. Why is a certain amount of genetic diversity favorable for reproduction? what exactly is a healthy distribution, and is there any discrepancy between normal and what is naturally occurring?

  8. This could be huge. It seems as though the majority of people inherit all of their mitochondria from their mothers, but if it's possible for paternal inheritance, it raises a lot of questions. Even though it's obviously far too early to say anything conclusive, this is something I'll be watching out for.

  9. I wonder how this may relate to the ancient cross-breeding event(s) between humans and neanderthals. Nobody alive today has mitochondrial DNA from Neanderthals. This of course means that any such matings had to have been with "their" males and "our" females. But if mitochondria can survive from the male, it seems like perhaps there were far fewer such pairing than previously imagined.

  10. Makes me wonder if the Rh factor could be implicated in whether the father's mitochondria is killed off or not. Like an immune system triggered event.

  11. I can already hear the creationists who will use this news as "definitive evidence" that scientists were "completely wrong" about human history the whole time

  12. If it’s a passed on mutation causing this to happen, we might be able to find out it’s roots, and how common it was through ancient history

  13. scishow , the name should be side show for all the pseudo and fake science you have promoted , especially fake gender science and even after you found out it was fake you didn't go back and unfuck yourself and admit to bad science reporting , I really can only blame you for bad reporting your defiantly not scientist , just actors and bad journalist

  14. This is not new, there were evidence before in both chloroplast and mithochondrial DNA. However the percentage is pretty low, and phylogenetic trees can be inferred by mtDNA.

  15. Here in america, every doctor and every hospital I've EVER gone to were unable to diagnose anything, nor recognize anything. They do the same thing, draw my blood, and x-ray me while the blood work comes back clean, then kick me out the door with a fat bill a month later and either a, "Don't know" or "maybe it's a heart problem" Followed by a "don't know" when that too comes back clean too.

    Do I have to be the 1% or work for the government? Or is this doctor thing just a shame like "Freedom"

  16. And (a few of) the feminists are triggered. Their singular dominant contribution has been taken away. I am pro-fem, but you know someone will get pissed anyway.

  17. Clinically, most human mitochondrial disorders are caused by abnormal NUCLEAR genes, which are inherited in the usual manner. Also, most mitochondrial enzyme complexes are made of multiple subunits, most of which come from nuclear genes. So even when a defective mitochondrial enzyme exists that does contain one or more subunits that come from mitochondrial genes, it isn't necessarily the case that the mitochondrial genes are the ones that are defective. This is complicated to work out in each family.

  18. Hank stated that the mitochondrial mutation rate is slow, but that rate is certainly faster than the NUCLEAR gene mutation rate because the mitochondrial gene duplication enzymes lack error checking / repair mechanisms, and mitochondria lack the enzymes required to repair environmental and free radical DNA damage (referring to free radicals that escape the mitochondrial defences such as superoxide dismutase). Mitochondrial replication is regulated by the amount of energy produced as ATP, so mitochondria that inefficiently produce ATP tend to multiply more, increasing their proportion during the individual's lifetime, often causing symptoms and signs of disease to appear later in adult life rather than early in childhood, and mitochondrial diseases tend to get worse with each child born to a woman and with each generation because the "bad" mitochondria multiply more in the female reproductive tissues.

  19. In sperm, mitochondria are normally found only in the tail mid-piece, which doesn't penetrate the ovum, see the picture here:
    https://openi.nlm.nih.gov/detailedresult.php?img=PMC4038059_2046-2530-3-5-1&req=4
    so I'm rather confused how any paternal mitochondria can be passed on to the conceptus, or why there is a hypothesis proposing that paternal mitochondria are somehow selectively killed by the ovum. It seems more likely that a rare variant sperm may have one or more mitochondria abnormally present in its head, which thereby manages to penetrate the ovum along with the nuclear injection.

    Also note that mitochondria often have multiple copies of their DNA, not necessarily the same, so even a single paternal mitochondrion passed onto the conceptus could pass on multiple paternal variants of mitochondrial DNA.

  20. I want to know where on Earth this kind of diagnostic testing is available. The average doctor in my town doesn't care nearly that much.

  21. i got a really interesting question that´s bugging me and wrecking my brain: if as "recently" as 30-50.000 years ago there were different species of humans (sapiens, neanderthals, heidelbergensis, denisovans) and we know for a fact that at least part of our DNA comes from neanderthals, which evidence or DNA-hints/ riddles do we have that our other "cousins" didn´t shag up with each other or with us too?
    Also, if we got up to 2.5% of our DNA from neanderthals, do we have an estimate of how much we have of other human species?
    Also, if our DNA is almost identical to that of chimps (as much as 98%) – does it mean that different hominins interbred?

    Last but not least, what REALLY bugs me, if we had so many close relatives on the evolutionary tree of our family of homo living side by side, though regionally seperated, how is it that we have had this long and awesome multilateral development going, with sooo many theories and hypothesis on how our and our close cousins´ brains develop so rapidly that it must have to do with social development, how come that we don´t have more evidence of human civilization other than from early homo sapiens settlements up to the bronze age?

    its hard to believe that our so closely related cousins were almost, if not as intelligent as we are did not leave any marks of "civilization" behind, as the neandertals did.
    If Heidelbergensis, Denisovans and Neandertals were living side by side with Sapiens, they surely had more interconnection, like trade, early forms of farming, cultivating plants and animals, other than just pure foraging and hunting for food. Am I naive to assume that human evolution for the past 800.000 years must have led to civilization before the assumed rise of plant cultivation and animal cultivation as recently as 10.000 years ago????

  22. Is this info correct that a research lead by Mark Stoeckle at Rockefeller University and David Thaler at University of Basel reached to conclusion after analyzing "Bar code" of 5 million animal from 100,000 different species including humans that humans sprang from single pair of adult male & female and 9 out of 10 animal species sprang from the same single pair. "Bar code" is a.k.a mitochondrial DNA.

    I got this info from a video. The link is given below. This video published on 27 Nov, 2018.

    https://youtu.be/ISK3KnYqLXE

  23. So much wasted effort looking into things when GOD is the answer. He became the LORD for a reason. Now everybody wants to be a democrat and say things they shouldn't for views. What do I know though, I've only been a christian for 37 years….whatever.

  24. about time someone proved that 1 "eve" theory completely suspect. I mean its totally against founders syndrome to begin with anyway.

  25. This is a lie cause men don't have eggs and can't pass off their mothers mtdna. If that's true then why don't everybody have it from their fathers. I want to see proof not just you saying this.

  26. We have many gene sequences we do not use many and other things like plants can use more than us . meditations actual turned on a couple as well as living healthier and opposite shows that it acn be damaged and use less

  27. Scientists the Black women are the only organism that possess the mitochondrial eve of all variations of every different kind of humans being in the planet 😭

  28. Even if so, human history as deduced by mDNA analysis still matches up very closely to human history as deduced by  Y chromosome analysis.

  29. What if there is something in the autosomal DNA that works as some kind of trigger for mtDNA? Triggers mutations or functions? That would explain how fathers heritage would come into play. Smoking or pollution can trigger cell functions, maybe there are "byproducts" from RNA or DNA that influence mtDNA?

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