Monday, April 11, 2005

441: Stirring the primordial soup

Stirring the primordial soup:

Circumstantial evidence for the central position of RNA in the origin of life can be found in 'relic' pieces of RNA that hold a few of the most important functions in the cell. Perhaps the most convincing observation is that, in the synthesis of proteins on the ribosome, the key chemical event — peptide-bond formation — is catalysed solely by RNA, suggesting that primacy lies with RNA rather than protein. A major impediment to full acceptance of an 'RNA world' is that, although it can easily be imagined that a pure RNA machine (a proto-ribosome) can make proteins, there is no equivalent RNA machine to make RNA (a ribopolymerase). All the RNA we know is made by protein, leading to perhaps the original 'chicken-and-egg' problem of which came first.
Taylor proposes a model of the transition from free-floating RNA to encapsulated RNA, which may resolve the problem. Testable evolutionary hypotheses. Hurray!