Scientists Create RNA From Primordial Soup 369
Kristina at Science News writes "The RNA world hypothesis proposed 40 years ago suggested that life on Earth started not with DNA but with RNA. Now a team of scientists bolsters this hypothesis, having assembled RNA in the lab from a mixture that resembles what was likely the primordial soup. 'Until now,' Science News reports, 'scientists couldn't figure out the chemical reactions that created the earliest RNA molecules.' The new work started the RNA assembly chemistry from a different angle than what earlier work had tried."
Re:Abiogenesis.... (Score:5, Informative)
not that big of a deal (Score:5, Informative)
Ignoratio Elenchi (Score:5, Informative)
Demonstrating that another link in the evolutionary chain can happen without conscious intervention (spontaneously and mechanically) does not demonstrate the non-existence of an intelligent designer.
It, at best, removes a point that was previously used to defend ID.
But, logically, the inability to prove something does not constitute a disproof (that would be the fallacy of Argumentum ad Ignorantium).
Disclaimer: I am not an ID proponent. I am just a logician.
Re:Abiogenesis.... (Score:0, Informative)
Oh yeah, "informative." And my failed "Primordial Post" was offtopic? You mods are tetched in the head.
A flowchart might be helpful (Score:5, Informative)
Previously, the sticking point was that there was no logical way for the sugar (ribose) to spontaneously attach to the base. Organisms use enzymes to transfer a ribose phosphate group to a base, but of course, in the time before enzymes could be coded for, that wouldn't be possible. This sequence neatly sidesteps that, and also provides a more logical reason for phosphate to be involved; it is the reagent that attacks that tricyclic pyrimidosugar, breaking the bond to form ribocytidine phosphate.
Coincidentally, UV light deaminates cytosine to form uracil, which is where that second base comes from. This is why DNA uses thymine instead of uracil, by the way- as the archival storage medium for our genetic information, it would be unwise to have one base easily interconvert into another. The shorter expected lifetime of RNA means the interconversion is not a concern, though.
Re:One word.... (Score:3, Informative)
Contamination. 'Nuff said.
Obviously. I'm sure they never accounted and corrected for that possibility. After all, it's not like these people are the type who would know anything about basic experimental science or anything.
Sometimes even the researchers think it's contamination, but the story's too good for journalists to pass up. A memorable example:
"Scientists at University of Alabama sequenced a 130-nucleotide long mitochondrial DNA sequence from dinosaur vertebrae, and found that it was 100% homologous to mitochondrial DNA from turkeys. However, the scientists themselves 'remain quite sceptical of our own work' and noted that they had been consuming turkey sandwiches in the laboratory."
Even though the triceratops-turkey 'finding' was never published and eventually dismissed by the researchers, the false result was leaked onto the internet, where it can still be found today [enchantedlearning.com].
This RNA synthesis paper [nature.com], however, has no such caveats.
Re:rna vs dna (Score:5, Informative)
DNA (Deoxyribonucleic acid) is generally double stranded (classic double helix) and is more robust than RNA (ribonucleic acid) which is generally single stranded. Both use a base 4 code of triplets of certain additions to contain information (normally denoted C,G,A and T). However, RNA has a slightly different set of bases (having uracil in the place of thymine so U instead of T). Almost all life on earth uses DNA to store information in its long-term form and makes RNA when it needs to make proteins. This is a process known as transcription http://en.wikipedia.org/wiki/Transcription_(genetics) [wikipedia.org].
The primary reason why this discovery is a big deal is that there is a hypothesis that all life started out as using RNA and only later evolved to use DNA. This is known as the RNA world hypothesis- http://en.wikipedia.org/wiki/RNA_world_hypothesis [wikipedia.org] This is a very popular idea in abiogenesis research. There are number of avenues of evidence for thinking this: Essentially, the major problem with a DNA first model of abiogenesis is that DNA cannot normally reproduce itself without proteins. Moreover, DNA cannot produce proteins without the aid of RNA. However, properly chosen RNA strands can reproduce themselves without protein assistance. Moreover, RNA can directly mediate the synthesis of proteins. So if one can find a procedure that can plausibly produced RNA then one can handle most of the problems of abiogenesis in one fell swoop.
Re:Ignoratio Elenchi (Score:5, Informative)
Stop right there. You couldn't even make it half-way through the first sentence without being wrong about something, impressive...
:P) and the diversity of life, not where life itself comes from.
Evolution has nothing to do with the origin of life. Evolution is the concept that organisms change over time due to external forces/stimuli (be they natural or artificial). It has nothing to do with the origin of life whatsoever, period, end of story.
Evolution is about the origin of species (an apt name for a book might I add
Re:rna vs dna (Score:3, Informative)
RNA, being simpler, surely came before DNA, but before RNA there'd have been much simpler self-replicators:
http://www.youtube.com/watch?v=U6QYDdgP9eg [youtube.com]
The precursors to life would have been nothing more than chemical chain reactions that consumed other chemicals in the environment. Separate a number of these reactions from each other (all consuming the same chemicals - i.e. competing - in the environment) and you've got the beginnings of evolution. Anything as complex as RNA may have taken millions of years, or more, to evolve from these simple beginnings.
Re:I thought... (Score:3, Informative)
EYIAH*YIET? I don't get it. Anyway, there was no start codon there.
Re:Yet again, with the shitty article names (Score:3, Informative)
Its not as simple as putting compounds in a beaker and mixing it up. Its a series of steps. You still have to stop and purify and then do the next step, and that probably didnt happen in the ancient world.
Re:Abiogenesis.... (Score:1, Informative)
It's not advanced chemistry. I think the point is that the reactions were not that tricky, just a matter of throwing the right building blocks together at the right times and they linked up. Such building blocks very likely did exist in the primordial goo. "Hey look, we can create RNA in the lab with building blocks present in primordial Earth." means just that: They've found a series of chemical reactions that cause RNA to basically self-assemble out of simpler pieces. Now mind you they haven't shown it happened, or even that it COULD have happened, but it shows that you don't need fancy cellular machinery (proteins) to assemble genetic material, by demonstrating a possible mechanism by which RNA can self-assemble. Previously, nobody had gotten the parts of RNA to come together by themselves. Just because it was an experiment performed in a laboratory under controlled conditions doesn't rule out that it occurred in the primordial soup. Think of this as a proof of concept.
Re:I thought... (Score:4, Informative)
The convention is to write in the 5' to 3' direction and usually the sense strand. Unless I'm getting things backwards again (and I often am, can't keep left and right straight either) 3-TAC-5 in the antisense strand is what is actually used to copy the mRNA transcript, which is 5-AUG-3, the same as the sense strand 5-ATG-3. The t-RNA has UAC which corresponds to it.
So, unless I'm once again confused, that would be two types of backward.
Anyway, there is no message in any frame, nor on the complementary strand.
http://www.expasy.ch/tools/dna.html [expasy.ch]
5'3' Frame 1
EYIAH-YIET
5'3' Frame 2
NTSHISILR
5'3' Frame 3
IHRTLVY-D
3'5' Frame 1
SLNILMCDVF
3'5' Frame 2
VSIY-CAMY
3'5' Frame 3
SQYTNVRCI
and reversing the sequence, in case it was written 3-5 also had nothing
TCA GAG TTA TAT GAT TAC ACG CTA CAT AAG
5'3' Frame 1
SELYDYTLHK
5'3' Frame 2
QSYMITRYI
5'3' Frame 3
RVI-LHAT-
3'5' Frame 1
LM-RVII-L-
3'5' Frame 2
LCSV-SYNS
3'5' Frame 3
YVACNHITL
I also did a quick blast search of the human genome and came up with no hits. I started trying to set the parameters to allow for mismatches (I don't use it all that often) when I realized that I'm probably completely missing the joke.