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Prions Evolve Despite Having No DNA
An anonymous reader writes "Scientists from the Scripps Research Institute have shown for the first time that 'lifeless' organic substances with no genetic material — prions similar to those believed responsible for Mad Cow disease and similar, rare conditions in humans — are capable of evolving just like higher forms of life. The discovery could reshape the definition of life and have revolutionary impacts on how certain diseases are treated."
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Natural selection doesn't pre-suppose DNA. Anything which multiplies to produce copies of itself, which can degrade/mutate between generations can evolve just in exactly the same way. Selection pressures work exactly the same. So does the chain reaction effect of multiplication of the survivors, resulting in major shifts in characteristics of a population.
But the actual story is the bad news part of it. That using anti-prion medication probably won't work all the time as it would just breed a drug-resistant breed of prions by preference.
Definitely bad news. We can forget about having the "saviour" take a bath in the daily oatmeal for our protection :)
Quidquid latine dictum sit, altum videtur
It's time we recognized that the interesting things about "life" are all just products of the fact that all kinds of systems can convey self-replicating entities of some sort, and they tend to be interesting and undergo evolutionary processes and etc. Whether they are non-biological DNA bundles, cellular organisms, oddly folded proteins, crystalized clay, etc.
So where are the nefarious / useful engineered prions at?
It's a little more complicated than that. There's basically three properties that are both necessary and sufficient for evolution to take place.
* Some sort of fitness function
* Reproduction, largely based on the properties of the "parent"
* Imperfect reproduction, so that variation can be introduced
Once you've got those three items, you have the potential for evolution.
That said, it should be pretty obvious that basically any frequently-duplicated structure in the physical world, whether it be made out of DNA, protein, or metal and gears, is going to have all three of those items - the third just thanks to the physical world being imperfect. Note that it's not required that it be capable of duplicating itself - if all machines were built by copying older machines, we'd get to see "machine evolution" as people tended to copy the ones that worked better and throw away the ones that didn't.
Of course it's also worth pointing out that none of these requires that the item exist in a physical sense - you can meaningfully talk about memetic evolution, societal evolution, language evolution, joke and humor evolution, so forth ad nauseum.
Breaking Into the Industry - A development log about starting a game studio.
Rocks evolve too.
Hasn't this bullshit "claim" been dredged up enough already? It's just a bit of really weak sensationalism from an attention-whoring geologist.
He himself doesn't even believe this nonsense, and does say, towards the end of that article that obviously "being changed by your environment" has nothing to do with "evolution", but hey, why not get some free publicity?
sic transit gloria mundi
Not really related, but it is entirely possible for humans to be "alive" in a physical sense even after they are brain dead. As long as they are hooked up to respirators etc., they can be kept alive indefinitely. To date, no human being is ever known to have regained consciousness after brain death.
The _big_ catch here is that most physicians are not properly trained to test for brain death. Most physicians will just see a flat line on an EKG and declare the patient brain dead. I used to work at an organ transplant center, where there were technicians that went through a formal checklist to make sure the patient really is brain dead. It was not uncommon to find patients who did not meet the strict criteria. In the most dramatic example, a 3-yo boy was supposedly brain dead, and he was in the operating room, ready to have his organs removed. The technicians discovered that his pupils did respond to light, so they rushed him out of the OR. On the way back to his room, the boy opened his eyes and smiled. But then he went back into a coma and died 5 days later.
Needless to say, the boy's parents were furious.
This is misleading, and upon second reading, it is some overly-philosophical hand-waving.
Yes, prions do not reproduce through the conventional genetic mechanisms. From my understanding, they encourage, through some direct protein-protein interaction, other polypeptides to fold incorrectly.
Think of it this way. HIV and other genetic disorders propagate through normal reproductive means. Like, if a person with an extraordinary innate musical ability has a child, that child will probably possess a natural ability for music.
However, if a talented musician adopts a child and then teaches him how to read music and how to play instruments, he will probably grow up to be equally talented.
Prions are similar to the latter case. They are encouraging other proteins, who don't in themselves possess any malicious function, the fold in such a way to attack the host.
This isn't reproduction. The "parent" prions are not in anyway responsible for the actual formation of the "child" prions. They are just responsible for causing them to become malicious, making them more role-model proteins than actual parents.
But you’re no better. You insult the other side, and bring no arguments to the table. You’re obviously right... to us... but to them, you now just made it worse, making them protect themselves from your pointless attacks even more.
This time, I’ll do it for you:
The difference is, that Rocks have no fitness function. Which is the difference between undirected change and directed evolution.
But the next time, if you wanna act superior, bring an argument. Like a common basis, and proper logic on top of it.
Any sufficiently advanced intelligence is indistinguishable from stupidity.
Putting the perils of terming new knowledge "obvious" aside, it does seem obvious that evolutionary mechanisms would have to be preexisting for life to have indeed evolved. Since the most generic definitions of life I've seen boil down to providing some form of localized reverse entropy, evolution of the materials of that reverse entropy should be able to happen before the condition itself is actually achieved.
To draw an utterly meaningless comparison, you can certainly have a power supply without a computer, but good luck doing any computing without the power supply. If that makes sense. I should probably cut my breakfast rum down to under 5 shots.
"I believe in micro-evolution but not macro-evolution"
"I believe in centimetres, but not metres"
Why *wouldn't* it be likely?
Darwin of course knew nothing of DNA, and his theory of evolution says nothing about it. Darwin didn't put it this way, but the key requirements for an entity to evolve are:
1. The entity contains the information needed to replicate (self-description)
2. This information is subject to random changes (mutation)
3. The environment is hostile -- some but *not all* entities will be destroyed (survival)
4. Variations between individuals make them more or less likely to survive (fitness)
DNA-based life fits these restrictions, but so do entities which store their self-descriptive information in RNA, protein, or computer memory. It places no restrictions whatever on the existence of life chemistry based around other atoms than carbon.
You can make lots of chemistry arguments about why carbon is necessary, but you can't argue it on pure Darwinian grounds. As for your specific point in favor of carbon:
Carbon has lots of free valences, which allow it to act like a universal lego-block
Silicon has the same valence properties, and also forms a wide variety of complex molecules. Phosphorus and sulfur can have valences of 5 or 6 in certain situations. Now, carbon *is* special, but not in the way you've described.
You're correct. If they evolve, they HAVE genetic material; it's a bit of a tautology.
It might be noted that, before the 1950s, biologists generally argued that DNA couldn't be our "genetic material", because it's structurally too simple. The most widely suggested storage for this sort of information was proteins, because they are the most complex chemical structures in our bodies.
This hypothesis turned out to be wrong. But there's still an old hypothesis that in the early stages 4 billion years ago or so, the early "living" things on our planet were mostly based on proteins. It's hard to come up with good tests of this, though, because RNA and DNA don't fossilize well, and we have no samples of them older than 100 million years or so.
In any case, this story is really just about finding some evidence supporting the protein-based inheritance conjecture. It's apparently valid to some degree in our modern world. It might be more widepread than just prions, but we don't know.
Something that we have known, and which was summarized well by Douglas Hofstadter in "Gödel, Escher, Bach", is that our DNA doesn't actually contain a definition of the mapping of DNA to amino acids. That is done by the proteins that "transcribe" RNA strings into the amino-acid strings for the proteins. It would be possible, by doing a bit of swapping around of the active parts of those RNA-reading proteins, to use a different DNA -> amino acid mapping, and a few variants of this mapping are known in nature. The real complexity comes about from the fact that our DNA contains genes that produce the proteins that do this transcription. But without the already-existing transcription proteins in a cell, there would be no way to discover the mapping that we actually use, because the information isn't actually in the DNA. It's "distributed" between the DNA and the already-existing proteins in the cell.
Of course, such multi-factorial causation chains (with feedback) are far too complex for most of the media, even the scientific media. So we pretend that our DNA contains all the information needed to produce us. The biochemists have known for some time that this isn't really true, but they don't make a point of it, because it "would just confuse" most of the reading public.
OTOH, Hofstadter has had pretty good sales of his book. Any nerds or geeks here who haven't read it should do so. It'll teach you a lot of fun stuff about the extreme complexity of the universe we evolved in.
(Religious people who don't believe in evolution shouldn't bother. The book isn't really about evolution per se, but it'll still get you seriously upset or confused about the nature of the universe. ;-)
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Any matter has one mission and one mission only: to find greater order. If matter without DNA or any prior form of order couldn't achieve more order, then life would not exist. Things want to be able to interact with their environment more efficiently, and must evolve to do so.
All things in the Universe try to minimise the amount of energy they have. In some special cases, like crystals for example, this means becoming more ordered: the energy of each atom/molecule depends on its distance from its neighbours, with each "preferring" the lowest energy distance. Getting as many neighbours as possible at this distance is effectively packing spheres with that distance as their radius, which turns out to be the most efficient with ordered arrangements like hexagonal close packing, so that's what's observed. In the general case, however, the amount of order goes down, see http://en.wikipedia.org/wiki/Entropy . In fact, in every situation which becomes more ordered over time, Thermodynamics says that somewhere else there must be a system becoming even more disordered (as an example, if a system is minimising its energy by becoming ordered then it's exothermic: the energy its losing will come out as heat. This heat is itself disordered, and can disrupt the order of whatever it comes into contact with (which is why so many Physics experiments are done as close to zero Kelvin as possible). Also, the total energy such systems manage to lose is restricted by the fact that they are becoming more ordered, there is an "entropic cost" when becoming more ordered, which means that it requires energy to do and therefore the system must keep hold of that much energy to do it.
For a simple example of how becoming more ordered takes energy, try stretching an elastic band. The polymers it's made of would, in a totally disordered system, take "random walks", which is very degenerate (there are LOADS of ways to randomly walk a certain distance starting at a point A and ending at a point B is the distance AB is much shorter than the distance you walk, ideally A and B are in the same place). That's the band's preferred state, and as such it isn't particularly long. By stretching it, the distance AB goes up, so there are fewer random walks of the same length which satisfy these new positions. In the extreme case the distance AB will be the same length as the walk, and there would only be one valid random walk between them (ie. going in a straight line). It takes energy to stretch the band because you're making it more ordered, which it doesn't want to be.
If matter's mission is to find greater order then a stretched elastic band would never snap back ;)