Where do Mitochondria come from?

Yours came from your mother.

As to how they came to be part of the cell in general, that's still heavy on the theory.

I have been told that mitochondria can be infectious, spread from one person to another, and act in other bacteria-like ways. They are interesting, but, as was said, much about them is pure theory.

The wiki:

http://en.wikipedia.org/wiki/Mitochondria

And there's plenty more info on evolution at Talk origins.org.

We know where they are and where they come from. We've got a pretty good model of why and how they work. The theory comes in as to how and why they evolved and work the way they do. Evolutionary theory is that they evolved from symbiotic bacterial fragments or phages that adapted to live in harmony within our cells, but it's still just theory (if very sound theory with a lot of evidence to back it up).

please don't use that phrase "it's just a theory". In science:

A scientific theory comprises a collection of concepts, including abstractions of observable phenomena expressed as quantifiable properties, together with rules (called scientific laws) that express relationships between observations of such concepts. A scientific theory is constructed to conform to available empirical data about such observations, and is put forth as a principle or body of principles for explaining a class of phenomena.[1]


A scientific theory is a type of inductive theory, in that its content (i.e. empirical data) could be expressed within some formal system of logic whose elementary rules (i.e. scientific laws) are taken as axioms. In a deductive theory, any sentence which is a logical consequence of one or more of the axioms is also a sentence of that theory.[2]


In the humanities, one finds theories whose subject matter does not (only) concern empirical data, but rather ideas. Such theories are in the realm of philosophical theories as contrasted with scientific theories. A philosophical theory is not necessarily scientifically testable through experiment.

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From the wiki.

Maxx said:

TThe article is
kind of amazing in terms of its methods, most of which
are news to me (including the news that the HAL pipline is a series of Perl scripts)

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Most of bioinformatics runs on Perl - it's the perfect scripting language for handling DNA, which is basically just a ginormous string of letters

(My day job is as a web developer for a big bioinformatics project. Using mod_perl, obviously!)

It's a camel, not a muskrat

My commiserations on the number-crunching!

Snick said:

I have been told that mitochondria can be infectious, spread from one person to another, and act in other bacteria-like ways. .

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I've never heard of that, but that doesn't mean that it's impossible. (actually, it would be kind of neat if they could) If you happen to have a non-wiki citation, I'd like to see it.

GeorgeK said:

I've never heard of that, but that doesn't mean that it's impossible. (actually, it would be kind of neat if they could) If you happen to have a non-wiki citation, I'd like to see it.

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I only have that from a specialist in the field, but I have not seen anything in print about it. But I have learned that there is a huge amount of information that is only in specialized publications.

GeorgeK said:

I have been told that mitochondria can be infectious, spread from one person to another, and act in other bacteria-like ways.

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I've never heard of that, but that doesn't mean that it's impossible. (actually, it would be kind of neat if they could) If you happen to have a non-wiki citation, I'd like to see it.

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Here, let me google that for you:

Mitochondrial Capture by a Transmissible Cancer

If you don't have a subscription to 'Science' - here is a very readable summary:
http://blogs.discovermagazine.com/notrocketscience/2011/01/20/contagious-cancers-switch-their-batteries/

To quote:

The contagious cancer sometimes gets a glitch in its power supply, and it has to swap to a new set of batteries. Claire Rebbeck from Imperial College London has found that as the cells spread, they can pick up small structures called mitochondria. These are the batteries that provide our cells with energy, and the tumours can replace their set by raiding their hosts.

Mitochondria have their own small genome. Rebbeck looked at these little sets of DNA in 37 CTVT samples from four continents. Like Weiss and Murgia before her, she found that the cancer cells had mitochondrial DNA that was very different to that of their hosts. This shows, once again, that the tumours had spread from dog to dog, rather than rising up independently in each animal.

But Rebbeck also found that her mitochondrial sequences were far more diverse than she expected. When she drew a family tree of their evolutionary relationships, she found that the samples fell into two big closely related groups, with three black sheep that sat on their own (see the red boxes below). And when she did the same thing using DNA from the tumours’ main genomes, she got a different pattern.

This strongly suggests that the contagious cancers are occasionally picking up mitochondria from their hosts. They have done this many times, ever since the original cancer cell broke free for a life of independence. This probably happened around 10,000 years ago, although the ancestor of today’s tumours probably arose just 250 to 2,500 years old. That still makes CTVT the oldest lineage of mammal cells still around.

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Wikis have great summaries - with links to the respected sources that you can confirm the data on.

It is a shame that you don't want to read them. You are missing out on a lot.

Mac

Mac H. said:

Here, let me google that for you:

Mitochondrial Capture by a Transmissible Cancer

If you don't have a subscription to 'Science' - here is a very readable summary:
http://blogs.discovermagazine.com/n...20/contagious-cancers-switch-their-batteries/

To quote:



Wikis have great summaries - with links to the respected sources that you can confirm the data on.

It is a shame that you don't want to read them. You are missing out on a lot.

Mac

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Thanks for the link, and no I don't have a subscription to, "Science."

The articles refer to external cells capturing mitochondria, which is very different than mitochondria being, "infectious," or being able to spread on their own.

No, I don't care for wiki because there are a few subjects on which I am an expert, and have even been in court as an expert. When I've perused wiki on those topics they were terribly innaccurate. Usually it was so oversimplified that it became wrong. Other times it was just flat out wrong and clearly edited by someone with political motivation behind it. If you think about their basic concept, no real expert is going to have the time or energy to go write and then edit and re-edit and re-edit wiki. They'll be busy doing that thing in which they are the expert. It's like the creators of the website decided, "Hey, let's get experts who want to write for free and have the time to do it!"

If I know that I can't trust wiki in the things I do know, why should I trust them for things of which I'm not as sure? In my estimation, I'm not missing out on much, because if the information is suspect, then it's mainly a waste of time. Most legitimate medical journals have articles that are for the most part only worth skimming. At least 80% of the articles in good journals are next to worthless because of poor statistics or obvious erroneous assumptions and that is a higher standard than wiki.

GeorgeK said:

The articles refer to external cells capturing mitochondria, which is very different than mitochondria being, "infectious," or being able to spread on their own.

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It is about mitochondria in the cells of one animal passing to another unrelated animal.

You can argue that they don't pass on their own .. they only pass to unrelated animals inside host cells .. but isn't that still infectious?

Obviously not every mitochondria in every cell of the new host's body is going to be changed to the new one - but it would certainly seem to fit the description of 'infection' to me.

No, I don't care for wiki because there are a few subjects on which I am an expert, and have even been in court as an expert. When I've perused wiki on those topics they were terribly inaccurate. Usually it was so oversimplified that it became wrong. ... At least 80% of the articles in good journals are next to worthless because of poor statistics or obvious erroneous assumptions and that is a higher standard than wiki.

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Exactly. A wiki is just as bad as any other oversimplification.

An old study compared the accuracy of science articles in Wikipedia (as judged by experts in each field of science) and compared them with the same expert opinion of equivalent articles in Encyclopaedia Britannica.

It was terrible. Encyclopaedia Britannica had about 2-3 errors PER ARTICLE. Wikipedia was just as bad - it was marginally better but the difference wasn't statistically significant.

Yes - comparing a wiki to a Good journal is always going to miss out on accuracy. But comparing it to a world class encyclopaedia? Sadly - they come out pretty equivalent.

The big advantage of the wiki is that the reader KNOWS it is inaccurate. Can you imagine the ignorance that was being peddled by those who read the Encyclopaedia Britannica and somehow thought it was accurate!! I bet they read the articles and sneered at their colleagues who instead looked up info on Wikipedia .. and then went to the extra step of checking the sources. Who would have more knowledge in the end?

As you point out 'In my estimation, I'm not missing out on much, because if the information is suspect, then it's mainly a waste of time.'

Yet if you read a respected Science Journal .. 80% of the articles (by your calculation) are suspect. So what is there left?

Mac

Mac H. said:

Yet if you read a respected Science Journal .. 80% of the articles (by your calculation) are suspect. So what is there left?

Mac

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20%, however to figure out what's wrong in wiki, you have to read the whole thing. In scientific articles you can read their methods and reject the article in a couple minutes, so your time saving is improved. It's not arithmatic, it's logrithmic in time saving when you can easily see the methods and statistics used to deduce the conclusions.

Mac H. said:

The big advantage of the wiki is that the reader KNOWS it is inaccurate.
Mac

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That would be a saving grace, if only people really did realize that, but most don't. Just like an encyclopoedia, wiki is for many things an adequate starting point to research a topic. It is not, however, an authority on anything. Unfortunately, I keep seeing more an more, people touting it as if it were.

Mac H. said:

You can argue that they don't pass on their own .. they only pass to unrelated animals inside host cells .. but isn't that still infectious?
Mac

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No, not by a longshot unless you assume that if someone knocks a bird's nest down and raises the baby bird to adulthood, that it was the baby bird that orchestrated the entire thing.

But Maxx,
the dangerously oversimplified theory (see the above discussion about oversimplification) is that at some point there were two different cells, one that exuded a lot of energy by way of phosphorus metabolism and one the fed off the energy by utilizing the phosphorus compounds. Somehow a symbiosis developed whereby the mitochodria got enveloped by the larger cell without getting eaten and became an organelle in return for protection.

There are many problems with the theory on the cellular and subcellular levels, but that is the thinking point that people point at.

A good rule of thumb used to be that if wiki said one thing, find 2 more sources that say the same thing to back it up. Today, with all the misinformation leaking through the walls, find 5 other sources that say the same thing or ignore wiki altogether in favor of actual open source science sources.

The Unseen Moon said:

please don't use that phrase "it's just a theory". In science:


From the wiki.

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While we're being picky pointing out such distinctions, please don't use wiki as an abbreviation for Wikipedia (or if you absolutely must, maybe you could capitalize it, as in "Wiki"). A wiki is generic name a user-editable website. Wikipedia happens to be the largest and most well-know such site.

Mac H. said:

It is about mitochondria in the cells of one animal passing to another unrelated animal.

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I misread this as "undead animal."

The Unseen Moon said:

please don't use that phrase "it's just a theory". In science:


From the wiki.

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Yeah. Well, theories are a dime a dozen and many of them SUCK so a heaping help of skepticism is warranted as is the phrase "It's just a theory" because after all, if it were such a truth of nature there would be irrefutable evidence.

(Or at the very least, enough to actually prove your point and I can think of several dozen theories off the top of my head that would never in a million years meet that threshold and the origin of mitochondria is one of them.)

"Theory" has become such a tricky word that sometimes I wish we would just strike it altogether.

Conversationally, "just a theory" has a specific meaning. For instance, I think the reason my husband is always running late in the morning is because then he has to stay late at work and miss putting cranky kids to bed. But that's just a theory.

Scientifically, "just a theory" implies a judgment of the evidence. It would be better to state what, if any, the dissenting opinions are. Are there studies in peer-reviewed journals that refute the theory, or support an alternate theory? Some theories are widely accepted as truth, some are not.

Sorry for the derail. Pet peeve.

Sarah Madara said:

"Theory" has become such a tricky word that sometimes I wish we would just strike it altogether.

Conversationally, "just a theory" has a specific meaning. For instance, I think the reason my husband is always running late in the morning is because then he has to stay late at work and miss putting cranky kids to bed. But that's just a theory.

Scientifically, "just a theory" implies a judgment of the evidence. It would be better to state what, if any, the dissenting opinions are. Are there studies in peer-reviewed journals that refute the theory, or support an alternate theory? Some theories are widely accepted as truth, some are not.

Sorry for the derail. Pet peeve.

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Even though The Unseen Moon piqued one of MY pet peeves by using wiki for Wikipedia, he's absolutely right about use of the word theory.

A scientific theory is BY DEFINITION widely accepted as truth.

Your "conversational" or colloquial use of the word theory is more akin in meaning to the scientific term hypothesis.

I'd lead the way with more examples of a word having several meanings, but it would surely go over like a lead balloon. It's enough to make one dazed and confused.

benbradley said:

A scientific theory is BY DEFINITION widely accepted as truth.

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You are absolutely correct. Sorry 'bout that.

A hypothesis with enough evidence to become widely accepted as truth gets promoted to theory.

In that sense, I suppose there are topics in which the proper debate is not whether the theory is valid, but whether the hypothesis has enough evidence to constitute calling it a theory in the first place. Bring in common vs. scientific meanings and it can get thorny. This is particularly problematic when the distinction between hypothesis and theory has huge political implications, e.g. global warming.

benbradley said:

A scientific theory is BY DEFINITION widely accepted as truth.

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And more often than not, there is a "competing theory" which basically derails the concept of "widely accepted as truth". I think "accepted as our best understanding of this thing" would be a better definition. Even in the case of E=MC2, the best we can say is that it matches behaviors in the universe when examining the macro scale and it's about as widely accepted as you get.

Don't get me wrong, I respect the scientific process and am a big fan of scientific study. But, in the end, a theory is just a theory.

Hallen said:

And more often than not, there is a "competing theory" which basically derails the concept of "widely accepted as truth". I think "accepted as our best understanding of this thing" would be a better definition. Even in the case of E=MC2, the best we can say is that it matches behaviors in the universe when examining the macro scale and it's about as widely accepted as you get.

Don't get me wrong, I respect the scientific process and am a big fan of scientific study. But, in the end, a theory is just a theory.

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I think you're missing the point about the distinction between scientific theory and regular old theory. If a scientific theory is, by definition, widely accepted as truth, that means that if a competing hypothesis comes along with evidence to back it, the "scientific theory" gets demoted to "just a theory" which is, in scientific speak, not a theory at all, but a hypothesis.

Guess as to how things work = hypothesis, aka, "just a theory" in lay terms
Best guess = best hypothesis.
Guess with a broad body of evidence to support it, widely accepted by the the scientific community = scientific theory.

See how it gets confusing?

Remember that by definition a scientific theory also must be falsifiable, meaning that it could be contradicted by experiment or observation. That's why evolution is a scientific theory, but intelligent design is not. Yet they are both "theories" in the lay sense of the word.

Sarah Madara said:

"Theory" has become such a tricky word that sometimes I wish we would just strike it altogether.

Conversationally, "just a theory" has a specific meaning. For instance, I think the reason my husband is always running late in the morning is because then he has to stay late at work and miss putting cranky kids to bed. But that's just a theory.

Scientifically, "just a theory" implies a judgment of the evidence. It would be better to state what, if any, the dissenting opinions are. Are there studies in peer-reviewed journals that refute the theory, or support an alternate theory? Some theories are widely accepted as truth, some are not.

Sorry for the derail. Pet peeve.

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Let's go Anglish!

Hunch - a supposition prior to conclusion of experimentation of how a hypothesis (or learned guess) might fail or pass.
Guess - a supposition following the conclusion of experimentation
Learned Guess - a supposition used to conduct experimentation
Belief - a position taken at the conclusion of experimentation
Guesspell - an appraisal of positions, reviewed and critiqued by peers
Law - a further appraisal of positions, reviewed to such a degree that it is believed to be axiomatic (save for extreme conditions) by the majority of peers.