The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system is the latest RNA-guided, endonuclease tool in genome editing which allows for very specific genomic disruption and replacement. Cas9 Nuclease nuclear localization sequence (NLS), S. pyogenes, is an RNA-guided endonuclease that catalyzes site-specific cleavage of double stranded DNA. Guided by a targetspecific, single guide RNA (sg RNA), the Cas9 Nuclease NLS Protein serves to cleave both strands of a DNA duplex upon recognition of the target sequence by the sg RNA. The resulting double-stranded break gets repaired by the nonhomologous end joining (NHEJ) pathway, leading to a disruption in the open reading frame of the targeted gene. Cas9 Nuclease NLS contains a SV40 T antigen NLS on the C-terminus of the protein. Incorporation of a nuclear localization signal (NLS) aids delivery to the nucleus, thus increasing the rate of genomic DNA cleavage.