For the first time, experiments in evolution have produced an RNA molecule that can build other RNA molecules that are longer than itself.

Many theories of the origin of life rely on RNA self-replication, but researchers have struggled to make RNA 'enzymes' that can stitch together other RNAs of a similar size. Reasoning that freezing temperatures would stabilize RNA synthesis, Philipp Holliger and his colleagues at the Medical Research Council Laboratory of Molecular Biology in Cambridge, UK, ran in vitro evolution experiments in ice, producing RNA enzymes that can synthesize RNA at temperatures as low as −19 °C in tiny pockets between ice crystals.

By combining cold-generated mutations with those from previous work, the researchers created the most-efficient RNA enzyme so far: a 202-nucleotide molecule that can copy templates as long as 206 nucleotides. Ice could have aided the emergence of self-replication in the prebiotic chemical world, the authors say.

Nature Chem. (2013)