Figure 3.

RNA-guided genome editing with engineered type II CRISPR/Cas9 system and its application in genome-scale screening assays. (A) DSBs induced by nuclease Cas9 (yellow) and its sgRNA (blue and red) can be repaired in one of two ways. In the NHEJ pathway, the ends of a DSB are processed by endogenous DNA repair machinery and rejoined, which can result in random indel mutations at the site of junction. Alternatively, a repair template can be supplied to leverage the HDR pathway, which allows precise editing. (B) Genome-wide functional screening can be facilitated by mass synthesis and delivery of guide RNA libraries in viral form. The resulting mutant cell libraries will be selected under certain desired pressures. Last, the final cell populations will be sequenced to identify the sgRNAs and corresponding genome elements.