Early RNA Life

I think we have a winner. Nosy I posted the riddle to show that what I have been saying about DNA is true. If RNA could be synthesised viri wouldn't need a copy of DNA to replicate. DNA can synthesise RNA, so the only way to synthesise RNA is to have DNA do it for you. Thus there can be no self replicating RNA. Stop talking to me in a condescending manner, and maybe we can discuss this in a straight forward fashion. If not I can stop this now and write you all off as religous zealots.

That's simply not the case. RNA can synthesize RNA. Most viri just have RNA, so they don't have copies of DNA at all. They don't use the cell's DNA, they hijack the rest of the machinery to directly duplicate their RNA and the rest of the virus body. Viri have no cell machinery of their own.You're very much mistaken. RNA can synthesize RNA.

It seems, Bob, that the question isn't settled yet. I think you have to ask Crash to back up what he states but, IIRC, he is actually a biologist working in this area. He is unlikely to be wrong but we'll see what his back up his.It does appear, from your posts so far, that you are making statements in a complex area that you don't really have expertise in. You should be a bit careful about that.I'm afraid we've wandered rather a long way from the original topic.

Hrm, looks like I've been getting too big for my britches again.No, I'm not a biologist. My wife is a graduate student in entomology and I've taken a couple of courses in biology, but my major is English, angling for Journalism sometime in the future.So, yeah. Don't take my word for anything; I'm no authority and known to be wrong. Sometimes embarassingly so.

OK, but you made some clear assertions Crash. How do we settle the issue?

Hope this helps. Those viruses which use RNA as their genetic material use an enzyme called reverse transcriptase to make DNA from their RNA. These viruses are called retroviruses. The enzyme itself can be used in vitro and I've done that for years. When trying to clone a gene responsible for a certain protein which was inducible, cells were induced to produce high levels. That meant that they also were producing high levels of messenger RNA. Using reverse transcriptase a single strand of DNA was made in a test tube using mRNA isolated from the cells. This was then made into double stranded DNA and amplified by PCR using specific primers. This is a bog-basic, standard tool in labs and has been aroud for years. If reverse transcriptase doesn't exist then someone will have to come up with a pretty good explanation as to why my experimental work actually succeeded in making DNA from RNA. Oh, and it was definitely RNA that was the starting material since I added the enzyme DNAse which destroyed any DNA present, leaving only RNA.Retroviruses make a DNA copy of their RNA sequence and that DNA copy is then used to make lots of RNA copies. So at the end you have loads of copies of RNA all ready to be packaged into new virus particles.All viruses hijack the replicating machinery of the cell they infect. Retroviruses have to carry the information for making reverse transcriptase since their host cells don't. I can't remember if any of these viruses actually carry the reverse transcriptase enzyme inside their coat or if they make it as soon as they enter the host cell (would depend on whether the RNA is apositive or negative strand).Sorry if this is off topic, but I felt I could add my tuppence-worth here.

Thanks Trixie,It sounds on topic, given where the topic has gotten.However, I'm not sure where we are in this side issue of not being able to synthesize RNA.Let me try to understand please.Crash is correct when he says that RNA viri do not use the cells DNA. However, they do make DNA as part of the viral replication process they run in the cell.If the above is true then RNA is being synthesized in these cells by the viri.Now, you also say: This says that the process can be carried out outside of living cells.So you use this method for synthesizing RNA. That is, RNA can be synthesized.In the RNA synthesis proces there is DNA produced as an intermediate step.Since synthesis (in this context) simply means to create through a chemical process the statment that RNA can not be synthesized is incorrect.So far it does seem to be correct that DNA is involved as part of the synthesis process. However, since that DNA is created by the RNA the RNA is "self replicating" whatever the means used to do it.Is the above all correct?Now the remaining question is about self catalyzing RNA? Does that involve any DNA in the synthesis?Are there any other pathways to RNA synthesis, Trixie?

Incorrect.Chemical synthesis of RNA is commonplace - if you want references, check the methods used by the two labs linked to above, one by me, the other by Crash. The method used does NOT use DNA, and does NOT use protein. Just chemistry, not biology.Honestly you might have an argument if only one or two lab groups managed to accomplish abiotic RNA synthesis; however, it is so common that there are dozen of companies based on the service of abiotic RNA synthesis, not to mention the countless labs that synthesize RNA themselves rather than pay for it.Perhaps you can provide a link to your reference so I know what you are basing your argument upon; I've done the same for you multiple times above.

Not necessarily. DNA intermediates are often produced for the sake of stability and efficiency. No DNA is required (otherwise RNA wouldn't have been chosen as the first replicator) - a reference list from my previous post: Chemical synthesis, as is used by labs and many companies, linked above by Crash and myself. No DNA or protein is used in this synthesis, only chemical reactions.

Some more details with references if you are interested, from yet another commercial RNA synthesizer: None of the processes listed involve DNA or protein.

Trixie Pretty much has it right, except she forgot to mention that reverse transcription has to be done, because RNA doesn't have the proofread capability that DNA does. RNA will quickly degrade, because of mistakes. DNA will proofread and correct. Thats why the riddle yes it can, and no it can't. That's one of the reasons a virus needs the cell to replicate.

But it seems, Bob, you are wrong. Care to comment on Pink's posts? He's the one I had confused with Crash and an expert in the field.This message has been edited by NosyNed, 11-07-2004 07:05 PM

the early evolution of life relies on the premise that some RNA sequences can catalyze RNA replication. Notice it says premise. This is not proven. Pink if you would post a little less technical I could better respond. You may even convince me I am wrong in my assumption that life must have been engineered. I got my info from the man who made his own virus Eckard Wimmer

Perhaps. But short RNA replicators (think less than 100 bases) don't need the 1 mistake per 1,000,000,000 bases accuracy that you get with DNA polymerases.From one of the references I mentioned previously; they used a short piece of RNA that itself had RNA polymerase activity. In other words, the short RNA acted like a protein enzyme. The RNA-based RNA polymerase was quite accurate: You also write: OR, it would quickly evolve because of mistakes. Incorporation of mistakes in say 10% of "progeny" replicators is not going to cause loss of the entire population, since it is likely that exponential replication would be going on at the level of millions and billions of replicators - not unlike bacteria.If you put a billion bacteria under antibiotic selection, the majority will die off, but a few will "evolve" resistance to the antibiotic, and quickly and exponentially proliferate to the numbers present in the original population.A similar scenario may have happened in the original RNA-based world - in fact, one area of abiogenesis research is the instability of RNA, and mutational effects of the harsh environment (such as radiation). The high level of mutation would have made evolution proceed faster, since occasionally a mutant would arise that was more stable than its predecessor. These stable mutants would likely be selected, and "take over" due to their increased stability, or other beneficial attribute. This cycle could continue to produce longer, more stable RNA "life" with multiple enzymatic properties.Hopefully that makes sense - let me know if you have specific questions.

But, as I pointed out back in Message 44 that article was from a telephone interview. We have no idea of the context of the statement, it's order in the conversation or even if that was exactly what was said.

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Aslan is not a Tame Lion