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In a sense we are RNA-based lifeforms. Our protein synthesis machinery is dependent entirely upon RNA. I think there’s a perspective here that the RNA world nev
by keithwhor 6y ago
In a sense we are RNA-based lifeforms. Our protein synthesis machinery is dependent entirely upon RNA. I think there’s a perspective here that the RNA world never disappeared, just became symbiotic with higher-order protein structures. On one hand, RNA viruses continue to replicate successfully (i.e. SARS-nCoV-2) and on the other we rely on rRNA, tRNA and mRNA to function as a highly-conserved part of cellular function across all organisms.
When I was in grad school my default assumption was that ribozymes (catalytic RNA) are far more abundant than we currently know. RNA just very difficult to work with so there’s a selection bias against our ability to measure its behavior in vivo.
- wombatmobile 6y ago> In a sense we are RNA-based lifeforms. Our protein synthesis machinery is dependent entirely upon RNA. Yes, we are RNA organisms that have been incorporated into larger organisms, just as we are prokaryotes that have been incorporated into eukaryotes through endosymbiosis. https://evolution.berkeley.edu/evolibrary/article/_0_0/endosymbiosis_04 https://evolution.berkeley.edu/evolibrary/article/_0_0/endos...
- keithwhor 6y agoAbsolutely the comparison I was intending to convey! Biology is a messy and beautiful place filled with competition and cooperation. :) As much as 8% of our DNA was laterally transferred from viruses! In a sense, some infections result in a symbiosis with a host. https://en.m.wikipedia.org/wiki/Endogenous_retrovirus https://en.m.wikipedia.org/wiki/Endogenous_retrovirus
- wombatmobile 6y agoLateral DNA transfer is awesome. Check out this visualisation of the molecular apparatus assembled on the surface of a bacterium to inject a chunk of DNA into a neighbouring bacterium. Type 4 secretion system: ii- Pilus biogenesis https://www.youtube.com/watch?v=ihlFqOK5cZM https://www.youtube.com/watch?v=ihlFqOK5cZM
- kolinko 6y agoWhat parent commenter was wondering - if prokaryotes didn’t die off when eukaryotes appeared, a question is why non-cellular life disappeared when cellular life appeared. Even if cellular life has a huge evolutionary advantage we should still find pockets of original life somewhere.
- est31 6y agoMaybe we can't find it because we don't know how it looks like? Maybe it's everywhere? If you dig up some dirt and sequence the genome, you find tons of DNA and RNA but for most we have no idea about what it does. Likely once we find the first pre-cellular life (if it exists), we'll figure out what to look for and then suddenly it'll appear everywhere.
- folli 6y agoI think you're basing this on a false premise. There's no rule that states that every life form that ever existed must have any descendants. In fact the opposite is true, the vast majority of life forms were exctinct. Famous case in point are the Ediacarean fossils in Newfoundland, the first known multicellular organisms. No descendants live today, they are completely extinct. Without these fossils we wouldn't even be aware of this branch of the evolutionary tree.