Modelling neutral and selective evolution of protein folding.

We examine a model evolutionary space consisting of genotypes mapped to their corresponding phenotypes. This mapping is derived from a lattice model for proteins which, despite its highly idealized nature, has been shown to share general properties with real proteins. Large evolutionary networks are observed, with genotypes corresponding to non-lethal phenotypes linked by unit mutational steps. Neutral mutations are necessary for traversing the evolutionary networks, and even one neutral mutation in a genotype can change the phenotypes attainable by a unit mutational step.