Genomic DNA was extracted using the PureLink Genomic DNA Mini Kit (Invitrogen). Specific genomic loci were amplified using Velocity DNA Polymerase (Bioline). Off-target loci represent the top predicted off-target sites in the CRISPR Design Tool (crispr.mit.edu)68 (link). PCR products were gel-extracted (NucleoSpin Gel and PCR Clean-up kit, Clontech) and sent for Sanger sequencing. Sequencing results could then be uploaded to the Synthego ICE Analysis tool (v3) allowing for inference of the percent indels in the sample. For deep sequencing, the gel-extracted products were pooled and prepared for sequencing via paired-end 2 × 150 bp iSeq (Illumina, San Diego, CA) sequencing in-house.