[The impact of neutral mutations on genome evolvability]

Beneficial mutations with strong effects are rare and deleterious mutations are purged by natural selection. Therefore, the majority of mutations that accumulate in genomes have very weak or no selective effects, being then called neutral mutations. Over the last two decades, it has been shown that mutations, even when they are neutral, affect evolvability by providing access to new phenotypes through later-occurring mutations that would not have been available otherwise. We propose here that in addition to this effect, many mutations -independent of their selective effects- can affect the mutability of neighboring DNA sequences and modulate the efficiency of homologous recombination. Such mutations do not alter the spectrum of accessible phenotypes, but rather the rate at which new phenotypes will be produced, a process that has long-term but also potentially short-term consequences for cancer emergence.