Theory on the evolution of mutation rates identifies three principal forces involved: the generation of more deleterious mutations with higher mutation, the generation of more advantageous mutations with higher mutation,
and the metabolic costs and reduced replication rates that are required to prevent mutations. Different conclusions are reached based on the relative importance attributed to each force. The optimal mutation rate of organisms may be determined by a trade-off between costs of a high mutation rate,
[10] such as deleterious mutations, and the
metabolic costs of maintaining systems to reduce the mutation rate (such as increasing the expression of DNA repair enzymes.
[11] or, as reviewed by Bernstein et al.
[12] having increased energy use for repair, coding for additional gene products and/or having slower replication). Second, higher mutation rates increase the rate of beneficial mutations,
and evolution may prevent a lowering of the mutation rate in order to maintain optimal rates of adaptation.
[13] Finally, natural selection may fail to optimize the mutation rate because of the relatively minor benefits of lowering the mutation rate, and thus the observed mutation rate is the product of neutral processes
