- Biological life
This article is about alternatives to the dominant RNA-world theories.
Objections to RNA:
- Crucial processes that we consider part of life could not have been carried out by a single polymer, and particularly not RNA. This is because these chemical reactions have rates ranging across 20 orders of magnitude.
- RNA cannot explain the emergence of genetic code. It would have been too long for RNA alone to find the mapping rules from 64 three nucleotide sequences to 20 amino acids.
Possible solution according to Peter Wills and Charles Carter: this process could have been carried out with a peptide-RNA complex. There is not just RNA but also 20 so-called “loading” molecules which allow RNA to bond with specific amino acids.
Interesting parallel with Gödel’s theorem: This RNA-peptides world is thought to be a good candidate by the two scientists because it has a tight feedback loop between the two kinds of compounds that they compare with the “incompleteness” theorem: that in any logical system that represents itself statements will inevitably arise that cannot be shown to be true or false within the system. There would be this kind of “inevitability” of life in their system.
Conclusion: “We should put only a few of our eggs in the RNA world basket”, Jannie Hofmeyr.