RNA-catalyzed evolution of catalytic RNA

An RNA enzyme with RNA polymerase activity was used to replicate and evolve an RNA enzyme with RNA-cleavage activity. The fidelity of the polymerase is sufficient to maintain heritable information over the course of evolution, with a succession of variants of the RNA-cleaving RNA enzyme arising that have progressively increasing fitness. The RNA-catalyzed evolution of functional RNAs is thought to have been central to the early history of life on Earth and to the possibility of constructing RNA-based life in the laboratory.