Precise Cas9 targeting enables genomic mutation prevention. Escherichia coli str. K-12 substr. MG1655

Introduction of additional mismatches between the gRNA "spacer" and the target "protospacer" can confer single nucleotide specificity to Cas9. This specificity may then be used to engineering a "mutation prevention system", in which Cas9 and a tuned gRNA are used to proactively prevent point mutations from arising within an organism or population of organisms.