Abstract: The CRISPR/Cas9 system,as a critical gene editing tool,has been used widely for the precise editing of genome sequences in a variety of organisms since its emergence,and it may generate the nucleotides deletion,insertion or replacement at specific targeted sites,thus changing the functions of encoding genes. Gene-editing technique based on CRISPR/Cas9 system will be applied into various biotechnology fields including biological breeding for producing a new generation of biotechnology products. Current research reports on CRISPR/Cas9 focus on the Cas9 protein structure and function,as well as the working principle of CRISPR/Cas9 system. As one of the critical components of CRISPR/Cas9 system,guide RNA is also the research hotspot in gene-editing technology fields,there are many article reporting that optimization of guide RNA resulted in the increase of editing efficiency and precision of CRISPR/Cas9. Therefore here we reviewed the research progress on guide RNA in CRISPR/Cas9 system,focusing on the sequence composition,structural characteristics and transcriptional ways of guide RNA,which is conducive to completely understand the characteristics of CRISPR/Cas9 system. Moreover,we discussed the effects of guided RNA on the gene editing efficiency of CRISPR/Cas9,which is beneficial in using CRISPR/Cas9 system. Finally,we prospected the future research trend of guided RNA,aiming at solving the current issues of using CRISPR/ Cas9 and optimizing the gene editing technology with higher efficiency and accuracy.

Key words: gene editing, CRISPR/Cas9, guide RNA