Fig. 1.

Application of CRISPR/Cas genome editing in gene functional study. CRISPR/Cas system has a diversity of application in gene functional study. Based the DNA double strand break (DSB) repair mechanism, CRISPR can directly cause gene knockout (silencing) by insertion or deletion of a couple of nucleotides and repaired by non-homologous end join (EHEJ); however, if the homologue-directed repair (HDR) happed, with a DNA donor, CRISPR/Cas genome editing can be used to replace an undesirable gene or over express (knockin) and an individual gene. If deactivating the Cas9 enzyme, and with transcription effector or other enzymes fused with the dCas9, CRISPR/Cas system also can be used to base editing, epigenome editing and imaging.