Figure 1
From: Applications of CRISPR-Cas9 mediated genome engineering
The CRISPR-Cas system. The CRISPR-associated endonuclease Cas9 could target specific DNA loci and make double-strand breaks under the guidance of the tracrRNAs:crRNAs duplex. The tracrRNA:crRNA duplex directs Cas9 to use two distinct active sites, RuvC and HNH, and cleave the target DNA complementary to the crRNA, which has an adjacent protospacer-adjacent motif (PAM).