The RNA worlds in context

Abstract

There are two RNAworlds. The first is the primordial RNAworld, a hypothetical era when RNA served as both information and function, both genotype and phenotype. The second RNA world is that of today's biological systems, where RNA plays active roles in catalyzing biochemical reactions, in translating mRNA into proteins, in regulating gene expression, and in the constant battle between infectious agents trying to subvert host defense systems and host cells protecting themselves from infection. This second RNAworld is not at all hypothetical, and althoughwe do not have all the answers about howit works,we have the tools to continue our interrogation of this world and refine our understanding. The fun comes whenwe try to use our secure knowledge of the modern RNAworld to infer what the primordial RNAworld might have looked like. © 2012 Cold Spring Harbor Laboratory Press.