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Do self replicating, independent RNA strands occur in nature? They are often used in laboratory experiments but I have not heard of any wild populations. I mean independent of other organisms and able to reproduce on their own in the environment. I.e., not just viruses or transcription RNA.

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    $\begingroup$ I believe what you are looking for is Autotrophic self-replication, and no one has not been discovered, but that makes a lot of sense since the source molecules such a replicator would use are valuable biological molecules quickly gobbled up by bacteria. Prior to the evolution of these bacteria however that would not have been an issue. And as Rodrgo mention the replicator itself would be helpless food for any bacteria. This is why laboratory studies are so important since the can be done in the absence of bacteria. $\endgroup$ – John Mar 12 '17 at 5:00
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They probably existed in the beginning of life (on Earth or somewhere else). But any free RNA now would be almost immediately devoured by bacteria or other organisms.

Bacteria are ubiquitous. That's one of the first things you learn in a microbiology course. We do this experiment a few times: open up a Petri dish far from a Bunsen burner, and in a few days you can see how many bacteria and/or fungus colonies have grown in the Agar. Any good microbiology book will show you this. I have none right now with me, but have just found a few links by searching for "bacteria are ubiquitous" on Google: Understanding Bacteria, The Purple Phototrophic Bacteria, Bacteria in Agrobiology: Plant Probiotics and Public Health and Infectious Diseases.

As for the science studying the origin of life, I recommend The Fifth Miracle: The Search for the Origin and Meaning of Life, by Paul Davies.

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    $\begingroup$ While the answer might well be correct, it would be important to have a reference to backup your claim. Also, you should probably address the question of viroids as it is, IMO, unclear from the OP's question whether viroids would be an accepted answer. $\endgroup$ – Remi.b Mar 12 '17 at 6:11
  • $\begingroup$ @Remi.b References added. IMO, "independent RNA" excludes parasites. $\endgroup$ – Rodrigo Mar 12 '17 at 11:09
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Kind of; they're called viroids. If you mean RNA that also catalyzes it's own replication independent of environment then I'm not aware of any that exist in nature But one could make the argument that all 'life' is simply self-replicating ribosomal RNA which exploits proteins to do other functions and DNA to store it's information more stably.

It's a bit arbitrary to exclude other cells as an environment though.

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  • $\begingroup$ Including the term "able to reproduce on their own in the environment" rules out viroids and all other parasites. $\endgroup$ – another 'Homo sapien' Mar 12 '17 at 3:34
  • $\begingroup$ Their environment is by definition in and around cells, it's an artificial distinction. $\endgroup$ – Artem Mar 12 '17 at 4:10
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    $\begingroup$ "independent RNA" excludes parasites. $\endgroup$ – Rodrigo Mar 12 '17 at 5:06
  • $\begingroup$ I also thought of viroids at first. The question of the OP is a little vague in the sense that it does not really allow us to know whether viroid would fit the category. I would rather disagree that "independent" means "not parasitic" and I would disagree to not consider another cell as not being ones "own environment". +1 $\endgroup$ – Remi.b Mar 12 '17 at 6:14

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