Dolly the Sheep not totally identical clone 115
Marillion writes "Dolly, the first animal cloned from an adult mammal
has variances in her DNA from her "Mother." " The variances in the DNA are actually in the mtDNA, or mitochondrial DNA. It's an interesting read if you are interested in cell biology/embryology.
Re:Alright, that's scary (Score:1)
Um, heart transplants? (Score:1)
We've swapped darn near every organ in the body, except the brain, amputated limbs, etc. Nothing affect who we are until you start fscking with the brain. But forget brain transplants, just wait until we get the tech to take a #D scan of the brain's cell structure, interconnections, and function and use that info to duplicate a functioning brain in software. Now that should sufficiently quash all remaining concepts of there being a 'soul'. And if the software brain can run within a really small computer case that can fit inside your skull, you can copy your mind to the machine, implant it into your freshly cloned body and be immortal! But it gets worse. The w4r3z kiddies of the future will create full clones of Cindy Crawford, etc. (when the tech becomes cheep) that could be created, "played with" and then disposed of (the matter reclaimed for the next "toy"). With cool remote 3D internal imaging equipment, someone could 'pirate' a copy of YOU, do what they will with it, then get rid of it untracebly. Is this a crime since the subjects aren't "real"? Ignoring this issue won't make it go away when the tech makes it feasible.
star wars (Score:1)
Telomers, clones, ageing (Score:2)
Note that telomerase is also present in many forms of cell immortalization, such as those which result in cancer.
If you want to look to defeating aging, you should look to http://www.geron.com , since they are the holders of the patent on human telomerase encoding.
In any case, it's well known in the biotechnology community that Dolly is going to be prematurely senescent due to the shortened telomers resulting in an advanced (by the age at which the cells were removed from the original "parent") cellular aging clock.
If you are young, you might get away with cryogenic preservation of predominantly undifferentiaed cells, probably epithlial cells extracted from your intestine, but if not, no clone will be able to restore your lost youth.
Re:question (Score:2)
DNA is usually stored by extracting it from cells, supporting it in a buffer solution of correct pH and concentration, and freezing it at -80C. The thing is that while DNA as a molecule is rather robust, DNA as a storage medium is not. The information in it is rather fragile under chemical attack (free radicals or nitrites) enzymatic attack (from DNAse enzymes say) or harsh conditions (UV light). You only have to break two chemical bonds to sever the molecule. That's just as permanent as cutting a video tape with a pair of scissors. The best place to store DNA is in a living, respirating, cell that will take care of the DNA and make repairs to it.
As to how long DNA can be stored with the sequence unaltered, we don't know yet. Watson and Crick published their paper about the physical structure of the DNA double helix in 1953. Large scale formal work with the information coded by DNA has only kicked into high gear since the late '70s, early '80s with PCR, Sanger sequencing, and restriction (DNA cutting) endonucleases. It's barely been 20 years so far.
Re:Mitochondria Mutation (Score:1)
Re:Mitochondria in general (Score:1)
As I read it, what you are asking about is what is known as a molecular clock. The idea of a molecular clock is using a macromolecule (DNA or protein) to date the time when an evolutionary event occured (like the most recent common ancestor of all humans today- mitochondiral eve.) In short, if we compare DNA sequences, we can find out how many sites they differ at. Then, if we know the rate of substiutions, we can figure out how long it has been since we all diverged.
I say if because its not at all clear that rates of molecular evolution are constant between different groups. It seems that things like generation time, metabolic rate, body temperature and maybe even population size effect rates of molecular evolution. So our (human) rate of molecular evolution might be an order of magnitude different from the number I already gave. And the precise value of this rate will determine the value given for the age of Mitochondrial Eve.
Re:Mitocondria IS A BACTERIA!! (Score:1)
You saw what the descoloda did to humans!
Exactly! (Score:1)
Re:Alright, that's scary (Score:1)
>Anything that isn't the result of your
>enviroment? Who gets to decide if something is a
>problem?
I would say that you do for yourself. the point is moot however, unless we can figure out a way to keep the brain from decaying, there's no point in doing a brain transfer.
wow.... (Score:1)
In response to what you said about Mitochondria, well, if you take any kind of worthwhile biology course (I mean, "biology," not the larger pool of highly diversified and specialized courses that fall under the scientific category of being a biology), you'll learn that mitochondrian are/were believed to have been seperate entities before being taken in by cells (they have their own DNA, etc.). So that I already knew. (Thank you for pointing it out, nonetheless.)
And I'm assuming they did mean to imply all of the spiritual over/undertones that were implied by that statement... because, the whole of Star Wars is that it's another great myth explaining the universe and the world as we know it. yay Star Wars!
Spermia do contain mitochondria (Score:1)
A sperm cell is rather tightly compartmented. The sperm's "head" contains the acrosomal vesicle (enzymes and other proteins for bonding with an ova's zona pelucida, or egg coat.) and a nucleus, containing the genetic material to be delivered.
Behind the head lies a midpiece, filled with mitochondria, and behind that, the flagellum. Basically, in fertilization, only the nucleus of the sperm merges with the cytoplasm of the egg, and the sperm's mitochondria don't get a chance to enter the fertilized egg.
Re:star wars (Score:1)
For what it's worth, some people think the mitochondria might have started out as wholly autonomous organisms, little bacteria that were subsumed by early eukaryotic cells. This is the story they give in Star Wars: The miti-chlorites live in a "symbiot circle" with the cells. I'll bet this is supposed to have spiritual overtones: Cooperation is good, while gratuitous strife--like the strife that keeps the Sith at each other's throats and hence restricts their number to two--is bad. The good side of the Force is epitomized by caring for others.
Beer recipe: free! #Source
Cold pints: $2 #Product
Re:Mitocondria IS A BACTERIA!! (Score:1)
A diffrent thought... If we could geneticly engenear Mitocondria could we add the features of a computer to it?
Forget adding hardware go 100% wetware.. No more worrys about batterys...
Of course if someone made a Mitocondria computer Virus the potental exists for a "Parasite Eve"
Or worse.... GPF in Mitocondria
A Correction (Score:1)
Normal fork. (Score:1)
Re:A few comments (Score:1)
Kris
Re:Maybe 20 genes not cloned. (Score:1)
Re:What else to clone (Score:1)
Worst case: some bad diahhorea for a few days.
Home Cell advantage? (Score:2)
Do we know why a given set of mt survives? Could we just chalk it up to a chemical "host cell advantage" that favors the host mt?
Has this method been tried with a host cell that has been cleaned of intracellular structures?
Will this process work in Kansas?
Re:Strong in the Force? (Score:1)
Regarding "what they found in Anakin":
1) It was "midichlorians" but--at least to me--it seemed pretty darned obvious they were trying to talk about mitochondria withut talking about mitochondria.
2) I agree it was quite Lame; I rather liked the idea of the Force being some mystical power like ki, not like something out of a bad ripoff of "Parasite Eve". :P
3) EVERYONE I know, when seeing TPM, made the comment "Does this mean Darth Vader is really Mitochondrial Eve in a man's body now? Does this mean Aya Brea was really a Jedi?"...taking the piss of the whole midichlorian thing. (Then again, it can be argued me and my circle of friends read too much manga, watch too much anime, and play too many Squaresoft games for it to be healthy. ;)
Off to forget about the whole midichlorian fiasco and go play Final Fantasy VIII because it came out today (yay!)...
Re:Not unexpected (Score:1)
One is that every egg cell has to face the risk of being injected foreign mitochondria during normal fecondation. If I'm not wrong, the plasma membrane of spermatozoa locks to the egg's one and opens up upon fecondation, allowing the nucleus (and possibly the mitochondria that lie behind it) to flow in. Therefore, the egg is likely to be exposed to male mtDNA which will not appear in the grown animal.
My guess is that male mtDNA, if injected, eventually disappears as mitochondria replication is not allowed in a foreign environment (the egg plasma is originally filled with female-only proteins).
It could be that male mitochondria in the female egg are not able to exchange proteins or other components (such as membrane lypids, for which they're not entirely indipendent), thus 'dying' for lack of 'maintenance'.
Re:Not unexpected (Score:1)
For an excerpt in another book that has a lot of good essays check out The Mind's I by Hofstadter and Dennett.
They're both excellent.
-lb
Doesn't matter, mtDNA is well debugged! (Score:2)
Normally you get mitochondrial DNA from your mother because she provides the egg and nuclear DNA from both parents. In the case of Dolly she got nuclear DNA from the prototype only, through cloning, and mitochondrial DNA from the sheep that provided the egg. The scientists could have taken an egg from the prototype as well (if it was a ewe), and thus have kept the right mitochondria, but I guess that would have confused the experiment.
The point is that it doesn't matter. Mitochondrial DNA should be very well debugged by now, so it shouldn't matter which one you have.
Pavlos
Re:Not unexpected (Score:1)
That's what I'm referring to as being some of the focus of the articles/books, etc.
Sorry I didn't specify earlier. -lb
Bahhhh (Score:1)
Makes sense... (Score:2)
Are these really clones? (Score:1)
Cloning always seemed to be to be the duplication of the body(or parts therof) with sped up growth and no mind/soul.
And they're NOT midichloreans... (Score:1)
Anyone else remember that demented little thread?
counter-nitpicking ^_^ (Score:1)
I just felt obliged to point out that while mtDNA may mutate faster, it is generally very nearly identical to the female parent, whereas nuclear DNA differs more from the parent because it is mixed half-and-half with that of the male parent. It's obviously not mutation, but it might explain where the idea came from.
Also, favorable mutations are propagated more quickly in nuclear DNA due to the advantages of sexual reproduction. If one defines mutation rate as changes in the genome over time, it might change the answer.
And finally, I have a question: is this higher mutation rate per nucleotide, per molecule, or a per organism? Nuclear DNA may be more stable, but there are a lot more potentially mutated nucleotides in a set of human chromosomes than there are in a mitochondrion.
Re:Ick... inbreeding (Score:1)
Re:Alright, that's scary (Score:1)
Do you really believe in this "scientific" propaganda ?
Do you really think you and your clone are the same ???
Just imagine you were cloned and you and your clone were alive. Can you see through its eyes ? Can you read its thoughts ? Can you feel its pain ?
No ?????
Then you are obviously two *different* persons. The clone might be physically identical to you but *NOT* psychologically. It's not your body that makes you a unique human being, it is your mind.
Besides, what's the point of cloning ? I mean, *WHY* would anyone want to do it ?
----------------------------- Insert favourite quote here -----------------------------
Re:counter-nitpicking ^_^ (Score:1)
And again, the mutation rates which have been measured are per nucleotide per year at silent sites.
Just an aside: No DNA in hair? (Score:1)
Can't a DNA test be preformed on a strand of hair? Or perhaps do you mean that a 'good' complete strand of DNA cannot be extracted from hair or nails?
-pos
Apropos of very little... (Score:2)
Isaac Asimov once wrote a ditty,
sung to the tune of "Home On The Range":
Oh give me a clone,
of my own flesh and bone,
with the Y chromosone
changed to X,
and when I'm alone
my very own clone
will be of the opposite sex.
I told ya it was apropos of very little,
but for the subject of clones...
--------------------------
Your Favorite OS Sucks.
^D
Re:Not unexpected (Score:1)
Well, actually no one ever told me that happens, but why shouldn't it? Since the nucleus enters the cell intact, there's no obstacle to keep them from slipping in. Also, I seem too recall that, unlike with other mammal sperms, human male nuclei enter the egg with their tail still on. It eventually gets 'melted' by enzymes, and it's one example of the egg reacting to foreign structures. Another one is the male nucleus itself, which dissolves after having triggered the female one into completing meiosis.
Isn't it more likely that the female mitochondria are THEMSELVES recognising and destroying the male mitochondria?
I don't really think so. As I said before, mytochondria are not 'living things'. We have almost complete maps of mt genomes and there aren't any enzymes that could do such things. Mytochondria are not even self-sufficient when it comes to maintaining their membranes, exchanging ions and they lack some key enzymes for respiration (is that the right English word for their main function?).
The fact itself that mytochondria relate to ancient prokaryotes is fascinating and certainly likely, but not yet proven. My hystology professor told me last year that there's still a circulating theory that there really aren't many mytochondria, but a single, long and crooked one that gets sliced so that it looks like many.
Of course, this sounds at least exotic, but shows how little we know about that.
If the key to male (in the case of Dolly, ewe's) mtDNA disappearing is in anyway related to the outnumbering of female mt's over male ones, it has to be related to the incapability to reproduce as female ones do.
It'd be also very interesting to know how much foreign mtDNA could be found in a 4-, 8-, 16-cell embryo. That'd allow our speculations to be proven or ruled out...
Getting always more intriguing!
Re:Not unexpected (Score:1)
A couple of things:
1) It has been postulated (and is, I think, a necessary part of the prokaryote-decendant theory) that a lot of mitochondrial DNA was actually snarfed by the nucleus - support for this postulate is precisely the fact that you mentioned - the nucleus provides a lot of supporting proteins/enzymes/etc. to mitochondria.
This means that the nucleus could easily also be producing the mitochondrial proteins for mitochondrial attack on self-non-similar mitochondria. Therefore this possibility is not ruled, at least not by that argument.
(2) I seem to recall 2 years ago that our biochemistry lecturer was adamant that we STILL didn't know what the majority of those nifty little Mitochondrial proteins did.
We have the genetic code, but certainly not the protein-encoded meaning!!! A statement "there aren't any enzymes that could do such things" is not necessarily true....there are a lot of proteins that still have unassigned actions.
(3) WHY are male mitochondria incapable of reproducing is exactly the question we are all hypothesizing about.
It isn't sufficient simply to say that they are (incapable) - of course they are, they're not present in Dolly!!!!! I'm simply trying to present one possibility (they get bashed by the other mitochondria).
** Sorry - that's just a little dig. If you shoot my theory down in flames, I'm gonna show you don't have one...
-Shane Stephens
Re: Didn't someone fight in the "clone-wars" ? (Score:1)
Yodafish speaks: It was a cool night on Tatooine, the cloned sheep was Schaermen we. We whipped from ours light Light sabers and began to shear it. They had higher mitokondriezaehlimpulse than VorlagenYoda all!
Re:Not unexpected (Score:1)
Mmmmh, I'd rather see that in a symbiontic key. I don't think it's easy to demonstrate the eukaryotic nucleus actually transcribes snarfed mtDNA, if not for the fact that mtDNA codons and tRNA differ from those the nucleus has. IMHO, it's more likely that mytochondria originally were 'smart' aerobic bacteria that found a convenient environment within an anaerobic one. Only the ones that were compatible with host cell structures, and that were able to take advantage of them while producing enough ATP, eventually came to 'live' in it. It looks like a gradual, Darwinian event to me, much more like a 'coincidence' than a transfer of nucleic acid.
Therefore this possibility is not ruled, at least not by that argument.
Of course it isn't! I'm sorry if I looked too assertive, but I'm sure that we don't have enough data yet to rule out anything. I just meant to make my point and, as i said before, we'd really need to take a look at what is or is not in early embryos to start understanding.
(3) WHY are male mitochondria incapable of reproducing is exactly the question we are all hypothesizing about.
It isn't sufficient simply to say that they are (incapable) - of course they are, they're not present in Dolly!!!!! I'm simply trying to present one possibility (they get bashed by the other mitochondria).
... Which implies a positive action... But male (ewe's) mytochondria might just be unable to reproduce, which is different from 'being bashed out', as is being infertile from being killed before you ever have sex... The result, of course, is the same.
** Sorry - that's just a little dig. If you shoot my theory down in flames, I'm gonna show you don't have one...
I do have one, yet I can't really be sure it's the right one! My theory comes down to this: transplant mytochondria from a somatic cell to an unfecundated (or recently fecundated) egg--- the mytochondria won't be able to reproduce in that environment, although they won't be destroyed by anything else... They'll simply age and disappear (or brcome undetectable) because of their inability to reproduce and to maintain theirselves...
Re:Not unexpected (Score:1)
Look - take it as given that these mitochondria don't reproduce (if they did, they'd be present in Dolly).
Right, now - WHY don't they reproduce? That's the question that you don't have a theory on.
WHY do they simply age and disappear? WHY are they unable to reproduce and maintain themselves?
Oh - and there are certain amino acid sequences on some transcribed proteins that specifically target these proteins to the mitochondria, which at least suggests that these proteins were never part of the general cell mechanism that were taken advantage of, but instead specific, required proteins that the nucleus started to produce instead of the mitochondria.
It is just as likely, in fact, that the DNA code changed AFTER mitochondria entered the cell, and not before - remember it's fairly likely that the prototype eukaryotic cell and the prototype mitochondrial invader looked pretty similar.
-Shane Stephens
Re:Not unexpected (Score:1)
Think of allergies. Random-generated antibodies eventually bind to molecules they've never encountered before. One might say, shit happens.
The fact that some anaerobic prokaryotic cells produced proteins that were compatible with foreign aerobic invaders, thus setting up/contributing to a symbiontic system, is simply Darwinian. Some other didn't, and didn't make it to eukaryotes.
Maybe you're right, I don't have a theory, if thinking that they might have receptors incompatible with carrier proteins isn't enough to make one. However, I don't really think I'll go any further in this discussion, as I have no evidence to answer basic questions:
1) How many cell divisions does it take male/ewe mtDNA to become undetectable? This is important to assess whether mitochondria get rapidly eliminated or slowly, steadily degrade and decrease in number.
2) Would mitochondria transplants from a somatic cell to one of another individual work? That could determine once and for all if an egg cell is a different environment than a somatic cell with respect to mitochondria (it is in 90% all other respects, actually).
3) Would the same happen with a family in-breeding? That'd help understand if there's an in-cell 'hystocompatibility' system which differs from individual to individual, has a hereditary basis, or doesn't differ at all.
I realize that if I don't have an experimental answer to these questions, I really can't say anymore than: "It just so happens that they die of 'natural' death. I don't really think they get killed."
Zut happens (Score:1)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Belgium HyperBanner
http://belgium.hyperbanner.net
Re:Zut happens (Score:1)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Belgium HyperBanner
http://belgium.hyperbanner.net
Alright, that's scary (Score:1)
That means that cloning becomes a way to cure some genetical diseases. Rich Man has genetical defect. Rich Man gets cloned. Clone ages as fast as Rich Man (remember that? Dolly's cells show signs as aging as fast as her progenitor.) Rich Man transplants his brain without chance of reject.
Now that is a scary possibility.
That, or maybe I've played Parasite Eve too much and I'm gittery when the word "Mitochondria" gets mentioned. :)
"There is no surer way to ruin a good discussion than to contaminate it with the facts."
Surprising? (Score:1)
~Caliban
Boys from Brazil (Score:1)
At least they have some clues about that weird cell aging that they found before.
Rick Rezinas
Re:Strong in the Force? (Score:2)
The mitochondria are small sort of independant cell-like structures contained within our cells. The thinking is that simple cells evolved into complex cells by subsuming other simple cells around them. It's a borg-like thing I guess. Anyway, these cells which started to live together took over different jobs within the cells, and the mitochondria got the job of converting molecules into energy for the rest of the cell.
So, on a strictly cellular level, the mitochondria are the mitigators of the "force."
What they didn't tell you... (Score:2)
sporty
---
And I shall call him, mini-me
Re:Strong in the Force? (Score:1)
This idea of Lucas, to recycle the scientific fact that the Mitochondria (the power plants of the cell) have their own DNA and thus might be symbionts to us in his fictive religion was far more annoying to me than the Jar Jar binks character.
I wonder if another fact, that Mitochondric DNA is passed from the mother only to the child, will be used too. This was useful to determine the gentic ancestor of humanity, BTW.
This doesn't really present a big hurdle (Score:1)
Re:Strong in the Force? (Score:1)
No big surprise (Score:1)
Re:Alright, that's scary (Score:1)
~Caliban
This is a job for- (Score:1)
Re:Alright, that's scary (Score:1)
I recall the article saying that the vast majority of genetic deseases/defects are carried by the nuclear DNA rather than the mtDNA. So, most likely, you would still have the same genetic defects as before. Hooptie
Re:Alright, that's scary---Well, perhaps not. (Score:1)
I'm not trying to deny that they might be able to do what you are talking about eventually, but we are no closer than we were in the first place to having the forever man.
We still have to learn how to replace parts of the DNA with other parts, (genetic surgery), and THEN clone.
Re:Alright, that's scary (Score:1)
What else to clone (Score:1)
I have read (don't know how true it is) that our digestive system is working only if a certain collection of bacteria settles in our intestines. A new born is supposed to get this bacteria from his mother.
I have no idea, about how individual that inteestine flora is, but it could form another factor to consider that has to be duplicated for a perfect clone.
Re:Um, heart transplants? (Score:1)
Then you'll have to start worrying about psychiatrists of the Redmond school, of course, but I wouldn't recommend open source for your brain, either.
And how about Active XX/XY? If your mother chooses Windows 3000 as an OS when you're born, you might feel a compelling urge to talk about your most intimate secrets whenever she asks, then pass out and reboot...
Ick... inbreeding (Score:2)
If two siblings bred then the sperm's mitochondria should, hypothetically, be identical to the egg's mitochondria, no? If so, would we still see the destruction of the sperm's mitochondria within the first cycle?
Or if not, how man degrees of separation(genetically) is necessary before the egg decides to reject the sperm's mitochondria? Cousin? Cousin once removed? Etc?
-AS
Re:Alright, that's scary (Score:1)
I do.
It's my code. I can recompile myself if I want.
Re:Not unexpected (Score:1)
Re:Slightly awry (was Alright, that's scary) (Score:1)
Well, that's what I meant, but rather than explain it all, I decided to cut corners for dramatic effect, if you will. Of course, Rich Man would have to wait 20 years (I mean, who wants to live through puberty again? Wait, I could drink Coke all I want, consider a McExtra health food and play D&D all day? I take that BACK!) and then get a brain transplant. Of course, he wouldn't get any more life expectancy, which is perhaps the Universe's way of telling us we can't be immortals just yet... :)
Thanks. Enjoy it!
"There is no surer way to ruin a good discussion than to contaminate it with the facts."
Re:Um, heart transplants? (Score:1)
Re:Are these really clones? (Score:1)
Hmmmmmm (Score:1)
F
Re:Doesn't matter, mtDNA is well debugged! (Score:1)
More than expected, but likely (Score:2)
Re:Alright, that's scary (Score:1)
It sounded like he was advocating species-wide recoding, not something on a individual basis. You could never convince everyone (ie, the species) to voluntarily alter their DNA; some of us are quite happy with our flawed genes.
*shrug* It doesn't look like that's what he meant after all, but it's what I read.
Re:Alright, that's scary (Score:1)
rid our race of stupid geneitic problems
Which sounds like you mean species-wide recoding, not changes to individuals. Perhaps I misunderstood.
Re:Telomers, clones, ageing (Score:1)
Re:Strong in the Force? (Score:1)
Kintanon
Re:Not unexpected (Score:2)
Just think about all the people having sex every day, if they all got it right 1 in 200 times we'd be swamped with little babies... Anyone know the actual statistics for that? 1 in 1000? more? less?
Kintanon
Seriously OT (was Re:Telomers, clones, ageing) (Score:1)
It's been fun watching Monsanto, duPont et al. squirming in Europe recently though. Their party line appears to be: GM crops are safe
Our poxy government kow-towed before them - it's been particularly unpleasant watching the spectacle of the Rev. A.R.P. Blair toadying up to Monsanto and telling the British public that they weren't to worry and if it weren't for GM the third world would starve and anyway all these important people hav promised him it's safe. Thankfully, the masses have revolted (and after salmonella, BSE et al. it's hardly suprising), those evil anarchists in Genetix Snowball and similar organisations have been destroying crops and it looks like GM in this country is going to have an even harder ride than anticipated (and remember, Monsanto hired Burston Marsteler (sp?) to do their PR - these were the guys who tried to tell the world that the Exxon Valdez was an unfortunate accident, no-one was culpable and it wasn't serious anyway).
Zaibatsu? Who needs 'em...
--
Cheers
Jon
Evolution of Mitochondria (Score:1)
Maybe 20 genes not cloned. (Score:1)
Not unexpected (Score:4)
Not linked (Score:1)
Of course she's different (Score:2)
I'm no scientist, but neither am I clueless on the subject of genetics, and I'm sure I'm not the only one that was fully aware of the mitochondrial differences in Dolly. In fact, I'm surprised that this is news. If there was anything other than the egg's mtDNA I'd have been astonished.
Remember the 'mitochondrial eve' story that first surfaced a couple of decades ago? The idea that a common ancestor could be traced through DNA is only possible because mtDNA is passed almost solely from the mother. Dolly didn't have a mother per se, so the mtDNA comes from the egg.
Mitochondria in general (Score:3)
Mitochondria are cellular components that produce energy for the cell. The best scientific guess on their origin is that they were one invasive bacteria, but they enhanced some cellular function and evolved into a symbiotic role within the cell.
As decendants of cells, they carry their own unique DNA and RNA sequences. Their DNA data set is much smaller than that of the host cell, mutates at a slower rate, and is only passed down the female line. The scientists are running into the part of the mitochondrial mechanism that ensures that mtDNA is passed along the female line. Simply, the mitochondria of the host egg are more numerous and better equipped to deal with intruding foreign mitochondria. It will only be a matter of time before scientists flood the host egg with healthy mitochondria from the cell(s) to be cloned, or deal with them by removal much in the way they deal with the nucleus..
Yes it is (Score:4)
What's interesting and surprising about this research is that NO mtDNA except that from the egg was found. This implies that the "foreign" mitochondria originally present were either actively killed off by something, or more likely, were not signaled to replicate at the same time all the "native" mitochondria from the egg cell were (because if they didn't replicate, they would become randomly segregated into the billions of cells making up Dolly, and would be lost). This would mean the signaling pathways telling mitochondria when to replicate are more complicated than we thought they were; i.e. we could now try to figure out what signal turns on the replication and why it only affects some mitochondria.
JMC
Re:Alright, that's scary (Score:1)
No true male clones? (Score:1)
This interesting part is that this only works for females!
Though I suppose that in theory, you could get much the same effect by using donor egg-cells by a female relative, as mitochondrial DNA is preserved pretty well through the generations. (i.e. you've got pretty much what your mother has, barring mutations.)
Re:Ick... inbreeding (Score:1)
1: Mitochondria are tagged upon the production of the spermatozoa, thus dooming them. This has interesting implications in that it would be a different mechanism that what would destroy those mitochondria in the fused egg.
2: Perhaps cellular mitochondria have a particular cytoskeletal connection needed to operate that foreign mitochondria cannot receive on fusion.
However, it is not yet know (AFAIK) which mechanism is used; perhaps it's something I have not listed.
Re:Not unexpected (Score:1)
...there shouldn't really be that much reason why male mitochondria can't exchange nutrients with the egg - remember that the female mitochondria end up thriving in a half-male/half-female environment...which may also preclude recognition of male mitochondria by the female egg.
Isn't it more likely that the female mitochondria are THEMSELVES recognising and destroying the male mitochondria? This also fits in with the whole theory that mitochondria are adapted prokaryotic cells - presumably prokaryotic implantation into eukaryotes began as a parasitic attack, and prokaryotes that actively ejected other prokaryotic attacks would have a selective benefit.
Intriguing, anyway!
-Shane Stephens
Re:Mitochondria in general (Score:1)
One of the major factors is that oxygen radicals (which are potent mutagens) are produced in high quantities in the mitochondira as ATP is produced to power the cell. Mitochondira also seem to lack some of the error checking mechanisms in DNA replication that nuclear DNA has avaliable to it.
A few comments (Score:1)
Growing a brainless clone is probably the simplest element. Regulator (homeobox) mutations can defeat the growth of most of the brain; although more developments must be made to keep the mutant from dying.
Gene therapy is not enough to cure aging (unless a radical method which can fix mutations in an entire genome is developed.)
Plants live for a long time because they are not as intradependent as a human. Plants often have giant tumors in certain parts, but because they are much more of a parallel structure, the rest of the plant can live; a human, on the other hand, is far more internally organized and possesses little redundancy. Thus, a plant can have half of its roots die off, and still have half the plant operate, while a human can hardly live with half its body.
Gene-based gamete selection is already developed, and has succeeded for not only simple things like gender, but in the avoidance of Hunnington's disease gametes. The major holdback is the primitiveness of artificial insemination (it takes many many tries to get it right.)
One must keep in mind that cloning, gene selection, etc... are merely scientific developments. They can be used for the betterment or for the destruction of society. Not developing the technology because some uses of it may be bad is not a wise thing to do.
Re:Ick... inbreeding (Score:1)
In other words, it should be pretty simple to test such a case. You wouldn't necessarily need a couple that would traditionally be considered incestuous.
Another possibility concerning why this happens is that the mitochondrial DNA is somehow packaged differently in the egg than in any other cell. Perhaps it gets tagged somehow when the egg is produced.
Re:Cloning/genetic engineering (Score:1)
...you pointed out that plants can live for a very long time. If you notice, plants that live for extended periods of time either get very LARGE (eg trees) or grow very SLOWLY (eg blackboys), but the point is that plants never stop growing.
And the stuff that is old; dies anyway. If you cut a tree down (please don't) you will notice the large section in the middle known as deadwood. This _is_ dead wood.
I don't know if the aging problem is truly surmountable, but the fact that tree parts grow old and die, and that to survive trees have to keep growing, may suggest that it's not.
-Shane Stephens
Re:Mitochondria in general (Score:1)
Re:Cloning/genetic engineering (Score:1)
True, but natural selection has favored genomes which produce children and then get out of the way at a certain point (and thus stop competing for limited resources.) We've got many millions of years of evolution with this selection pressure, and I'd be surprised if we don't find that we have a much harder task stopping/reversing the aging process than appears. In other words, aging may be actively selected for rather just being the eventual result of accumulation of errors, etc.
Slightly off topic but.... (Score:1)
Slightly awry (was Alright, that's scary) (Score:2)
So loosely, the cloned being starts of with cells the *same* age as the originator and then those cells age "normally". One of the problems with this is that clones start out with basically the same resources as a newborn, but are genetically coded to be older. This could theoretically cause stunted developement and a host of defects.
Besides that, there is the issue of neural aging and degeneration in the originators brain if there is a transplant. Not to mention the fact that a cloned genetically defective human will still have the genetic defect.
All those things aside, the scary thing to me is that somebody would consider cloning a human that would age prematurely. Seems particularly cruel.
Love the nick btw, I've got about 100 pages left to the Cryptonomicon. Gotta see if I can finish that up tonight.
Cloning/genetic engineering (Score:3)
What does this mean? This means that the clone might have different mtDNA, which generally doesn't matter. In a case where you care, you get an egg from someone with identical mtDNA (e.g., your sister).
Of course, there are a lot more issues here:
The ethics of the whole thing.
Being able to grow a brainless clone (or being willing to kill the brain of the clone).
Being able to transplant a brain without causing paralysis.
Defeating aging of the brain.
Personally, I think this is the wrong approach to this sort of thing.
Aging can probably be defeated through much less drastic measures (e.g., gene theorapy) once the process is fully understood. Think of how long plants live--there's no fundamental reason why animals must age.
Genetic disorders, excluding those caused by mutations, can be eliminated through controlled reproduction. Consider that we all have far more reproductive cells than we need. Hence, if I carry both a good and bad gene for something, why not eliminate all of my reproductive cells that carry the bad gene?
Of course, all this genetic engineering stuff already has a bad feeling associated with it, based on the last major attempt to eliminate "bad" genes. (I'm referring to WWII, of course.)
Re:Mitochondria in general (Score:1)
As such, their genitic makeup is totally separate from the host. You could remove all the mitochondia from a given cell, and stick in new ones... why? I have no idea... mitochondria are basically glorified power supplies...so long as they work, they do very little to influence the overall makeup of the underlying system... (I haven't ever heard of someone surving long enough to even be aborted with malfunctioning mitochondria)
Finally, mitochondria are passed down the female line for the simple reason that male sperm don't have mitochondria. Male sperm are not designed [in Kansas, evolved elsewhere] to do oxidative reduction, (Make ATP via Citric Acid Cycle) and therefore do not need mitochondria...
Finaly, as near as I can remember, (I haven't studied this part of biology in a while) foreign mitochondria are attacked, not by the mitochondria inside, but by the host cell itself... (if they even manage to get inside, which is highly unlikely...)
I guess I really don't see this as a great revelation that the scientists did not have a complete clone, and I am pretty sure that the scientists did not either... they probably were just verifying in a new way something that had been known for quite some time.
Don Armstrong -".naidnE elttiL etah I"
midi-chlorians (Score:1)
Not even Master Yoda has a reading that high.
Something else: (Score:2)
A current explanation for this phenomenon deals with the fact that mitochondria do not have complete genomes. Many of the genes of mitochondria have migrated to the main genome; thus, mitochondrial structures are a combined product of host and mitochondrial synthesis. A mechanism could exist that disallows foreign mitochndria from receiving the nuclear support needed to support and reproduce themselves.
Another theory is that there is a special differentiating flag on each type of mitochondrion. A glycoprotein on the surface could be used to identify the mt, much like human cells get identified.
So, umm... (Score:2)