On Sat, Jul 6, 2019 at 6:34 PM Lawrence Crowell < goldenfieldquaterni...@gmail.com> wrote:
*> The idea of the RNA world runs into trouble with the ribosome, which is > a hugely complex system of RNA and proteins* In the RNA world there would be nothing nearly as large and competent as modern ribosomes and there would be no proteins at all, there would just be short single strands of RNA floating in a sea of nucleotides. As far as I know nobody has yet found a RNA string that could catalyze the duplication of a string of nucleotides as large as itself, but they have found a RNA string called tC19Z that could reliably copy, without the help of proteins, RNA sequences 95 nucleotides long. And that is almost half as long as tC19Z itself. I find that encouraging. Ribozyme-Catalyzed Transcription of an Active Ribozyme <https://science.sciencemag.org/content/332/6026/209> John K Clark RNA sequences up to 95 letters no be anything as big as a ribosome or any proteins at all, there would be short single strands of RNA floating in a sea of nucleotides neucteatides On Saturday, July 6, 2019 at 5:04:40 PM UTC-5, John Clark wrote: >> >> On Sat, Jul 6, 2019 at 4:18 PM Lawrence Crowell <goldenfield...@gmail.com> >> wrote >> >>> > We have lots of hypotheses on this, but it is a point where >>> biological evolution loses explanatory power, just as general relativity >>> fails at the center of black hole collapse. >> >> >> I think that's the key point, Darwinian Evolution can't take over until >> you have a replicator of some sort, in fact I would say the origin of >> heredity >> is the same thing as the origin of life. That first replicator was >> certainly far simpler than anything alive today and it almost certainly >> didn't have any DNA in it. RNA is only single stranded not double as DNA is >> and it is usually much shorter too, and RNA would help in getting over the >> chicken or the egg problem. RNA can carry information, not as well as DNA >> can but it can do it. And RNA can act like an enzyme and catalyze >> chemical reactions, not as well as proteins can but it can do it. So the >> first RNA life would be very incompetent by modern standards but with >> Darwin you don't have to be perfect you just have to be better than the >> competition. >> >> In 1986 Nobel Laureate Walter Gilbert said in the journal Nature: >> >> "*One can contemplate an RNA world, containing only RNA molecules that >> serve to catalyze the synthesis of themselves. The first step of evolution >> proceeds then by RNA molecules performing the catalytic activities >> necessary to assemble themselves from a nucleotide soup*." >> >> However some people, like Chemist Graham Cairns-Smith think that even the >> RNA world, although far simpler than modern life, was still too complicated >> to be the first replicator aka the first life. Cairns-Smith proposed that >> the very first replicators were not organic at all but were clays were >> information was encoded in a pattern of defects in silicate crystals. In >> 1985 he wrote a book about it that is now online: >> >> Seven clues to the origin of life >> <https://www.krusch.com/books/evolution/Seven_Clues_Origin_Life.pdf> >> >> The problem with figuring out how life started is that chemicals usually >> don't have fossils, so even evolutionary biologist and militant atheist >> Richard Dawkins admits that although he likes the Cairns-Smith theory we >> may never be able to say this is definitely how life started and it >> couldn't have started any other way, the best we can do is find a plausible >> way that life *could* have started. >> >> John K Clark >> > > The complexity group at Santa Fe Institute has a 3 month course on the > origins of life. I thought about joining, but decided not because my plate > is already a bit full and frankly all we really have to go with are > hypotheses. The idea of the RNA world runs into trouble with the ribosome, > which is a hugely complex system of RNA and proteins. How that got going is > difficult to know. > > I had this idea about RNA interactions with carbon nanofibers. Could RNA > coil up around these and these could serve as some system for translation? > Maybe in time this became more complex with more RNA and proteins bound to > the system. Eventually this evolved into the ribosome. I looked this up and > found of course other had taken up this idea. > > LC > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/ff2e28bf-d34e-4100-8e03-8f5aea2b2a47%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/ff2e28bf-d34e-4100-8e03-8f5aea2b2a47%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. 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