The CRISPR/Cas9 system consists of two components: the Cas9 nuclease, which cleaves DNA at specific sequences, and a guide RNA (gRNA), which directs the Cas9 nuclease to the target sequence.
The gRNA is complementary to the target sequence, and the Cas9 nuclease cleaves both the DNA and the gRNA at this point. This creates a double-stranded break in the DNA, which the cell’s natural mechanisms can repair. However, if the repair is not done correctly, it can lead to a change (mutation) in the DNA sequence.