Fig. 4
From: Genetic tool development and systemic regulation in biosynthetic technology
a Each ZFN contains the cleavage domain of FokI linked to several zinc fingers which can be designed to specifically recognize that flank the cleavage site. b TALEN target sites consist of two TALE binding sites separated by a spacer sequence of varying length. c CRISPR–Cas9 is a two-component system composed of Cas9 and gRNA. Once Cas9 finds a PAM site if the gRNA binds to the DNA, a double break occurs three base pairs upstream the PAM