A new product line of gene-knockout kits using CRISPR technologies provides a solution for researchers to knock out a human gene at the chromosomal level. The latest tool in genome editing—CRISPR/Cas9—allows for specific genome disruption and replacement in a flexible and simple system resulting in high specificity and low cell toxicity. The CRISPR/Cas9 genome editing system requires the co-expression of a Cas9 protein with a guide RNA vector expressed from the human U6 polymerase III promoter. With the protospacer-adjacent motif (PAM-the sequence NGG) present at the 3? end, Cas9 will unwind the DNA duplex and cleave both strands upon recognition of a target sequence by the guide RNA.