Genome editing efficiency of oligonucleotide-directed mutagenesis followed by Cas9/sgRNA-mediated negative selection. (A) Design of target-matched sgRNAs for negative selection of edited targets in galK. (B) The editing efficiency of the galK mutation using single-, double-, triple-, and quadruple-base mutagenic oligonucleotides. Each bar represents the mean of three independent experiments. (C) Cleavage of both unedited and single-base-edited targets by CRISPR-Cas9 owing to mismatch tolerance.