A possible solution to the problem that since protein needs DNA and vice versa, life cannot have emerged without some sort of stepping stone molecule. The candidate molecule, as implied by the title, is RNA. This was only reasonable after the discovery of the Tetrahymena ribozyme - an RNA enzyme. Since this landmark finding, many other putative remnants of this ancient molecular world have been uncovered.

Indeed, telomerase (the essential component of most eukaryotic cells thought to play a role in ageing) is an enzyme with a catalytic RNA subunit. More importantly, the machinery that produces proteins, the ribosome is a mass of RNA and protein. One caveat to this picture is that the ribose sugars that form the backbone of RNA are difficult to form in abiotic conditions. It is possible that the more stable and easier to form peptide nucleic acid (or PNA) was the first genetic molecule.

  • See: Nelson et al PNAS vol 97 page 3868 "Peptide nucleic acids rather than RNA may have been the first genetic molecule"

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