Origin of Life

RNA Prebiotic Synthesis

When origin researchers moved from the living protein theory to the living RNA theory, they unknowingly took a giant step backwards. The decision to switch was made for two reasons: 1) conceptually RNA should be able to replicate itself much more easily than a protein and 2) RNA can under special circumstances regulate a few chemical reactions. This second finding solidified RNA as the natural choice for the first living organism. The hope was that it might be able to regulate its own synthesis and thus be a very effective self replicating molecule. Nevertheless, the living RNA theory has created a whole new set of problems that need a solution. Many are much more difficult than the problems created by the living protein theory.

1) The building blocks for RNA are harder to synthesize under plausible prebiotic conditions than amino acids. In fact, cytosine has never been synthesized. Cytosine is also absent from meteorites.

2) Unlike amino acids, two of the building blocks required for RNA (cytosine and ribose) are not stable and have very short lifetimes. It is unlikely that these molecules existed in the soup.

3) Just like proteins, the building blocks for RNA do not form RNA molecules unless water is excluded. Given the short lifetimes of many of the RNA subunits, the high temperatures required to exclude water just accelerate decomposition.

Next: RNA building blocks: Adenine and Cytosine

Previous: Prebiotic Protein Synthesis