Fig. 3. Simple principles of four gene editing methods. (a) The guide RNA recognizes the PAM sequence and cleaves the Cas9 protein in front of it. (b) The ZFN identifies the target sequence and the Fok I cleavage domain cuts the DNA. (c) The TALEN identifies the target sequence and the Fok I cleavage domain cuts the DNA. (d) The dsRNA molecule enters the cells and specifically degrades the homologous mRNA.
