A test tube based system of chemicals that exhibit life-like qualities such as indefinite self-replication, mutation, and survival of the fittest, has been created by US scientists. The researchers say their perpetually replicating RNA enzymes take us a step closer to understanding the origins of life on Earth, as well as to how life may one day be synthesised in the lab.

The system, created by Gerald Joyce and Tracey Lincoln at the Scripps research institute in La Jolla, California, involves a cross-replicating pair of ribozymes (RNA enzymes), each about 70 nucleotides long, which catalyse each other's synthesis.  So the 'left' ribozyme templates the synthesis of the 'right', which in turn templates the 'left' and so on, building each other via Watson-Crick base pairing.  

'This is the very end of the line, where chemistry starts turning into biology,' says Joyce. 'It's the first case, other than in biology, of molecular information having been immortalised.'