Fig. 2
From: Gene editing with ‘pencil’ rather than ‘scissors’ in human pluripotent stem cells
Gene editing procedure of typical programmable genome editing tools (A) The zinc-finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), or CRISPR/Cas9 nuclease recognize target sequence in genome (i.e., “site specific binding”) by zinc-finger domain, transcription activator-like effector (TALE), or single guide-RNA (sgRNA) respectively. (B) The ZFN / TALEN and CRISPR/Cas9 induce “site specific cleavage” of DNA via FokI nuclease and Cas9 endonuclease respectively. (C) Upon DNA damage by activity of endonucleases, innate DNA damage repair system repair DNA. Site specific gene insertion from donor DNA for knock-in is achieved by homology directed repair (HDR) and micro-homology mediated end joining (MMEJ). Insertion or deletion (Indel), leading to functional knock-out occurs by non-homologous end joining (NHEJ). Created with BioRender.com