The Cas9–sgRNA–DNA complex. Guide RNA is coloured red, target DNA strand in orange and non-target DNA strand in fuchsia. The 5′-NGG-3′ PAM trinucleotide in the non-target strand is highlighted in yellow.
The CRISPR-associated protein Cas9 is an RNA-guided endonuclease that cleaves double-stranded DNA bearing sequences complementary to a 20-nucleotide segment in the guide RNA.Cas9 has emerged as a versatile molecular tool for genome editing and gene expression control. RNA-guided DNA recognition and cleavage strictly require the presence of a protospacer adjacent motif (PAM) in the target DNA.
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