Mutation, Competition and Selection as Measured with Small RNA Molecules

Evolutionary success depends on two components of the phenotype: those that determine survival in the prevailing environment and those that establish the rate of producing viable offspring. The combination of these two determines the population trend called fitness. Species interact by competition for resources (predation or symbiosis); individuals of the same species influence one another socially, and the individuals themselves may be composed of large numbers of specialized cells, all containing the same genetic information, that have to cooperate with one another for the organism they compose to survive and reproduce. Evolution is a dynamic self-organization process in which causal correlations between the performance of the process as a whole and its component subprocesses are not identifiable. In Darwinian evolution, selection is complemented by mutation. Mutation can be studied quantitatively if selection is excluded by restricting amplification to a single replication round. Mutation rates can be measured and is defined as the probability of incorporating a noncognate base per incorporation event. Many quantitative insights into the nature of evolution have been gained from studying the model system provided by Qβ replicase. For quantitative studies of natural selection under controlled conditions, amplification of RNA by Qβ replicase is still unsurpassed.