Abstract：Abstract CRISPR/Cas system in many bacteria and most archaea consists of clustered regularly interspaced short palindromic repeats (CRISPR) and associated proteins (Cas) and confers adaptive immunity resistance against exogenous invading plasmids and virus. Due to its site-specific, high-efficiency, easy-operation and low-cost, CRISPR/Cas9 has developed into the third generation of gene editing tool after Zinc-finger nuclease(ZFN) and transcription activator-like effector nuclease (TALEN) and gained tremendous popularity from researchers around the world. In this paper, the research progress on CRISPR/Cas system from the classification, structure and molecular mechanism was first reviewed. The diversified development of CRISPR/Cas system, profound exploration of new CRISPR system as well as different strategies for eliminating off-target effect, and improving specificity and extending targeting range was summarized, such as expanding protospacer adjacent motif (PAM) region, optimum design of sgRNA, processing construction of Cas9 and a series of work. The review pointed out its reformation and latest applications in establishment of animal models, gene therapy of human diseases, genome-wide screening and preparation of animal breeding materials , it also forecasts the research interests and application prospects of this promising technology. This article gives a detailed description of basic information of CRISPR/Cas9 which may provide references for researchers in related areas to do some futher research and application.
