What are the main components of CRISPR-Cas9 technique?

CRISPR-Cas9 genome editing includes two key components: a single-guide RNA (gRNA) and a CRISPR-associated endonuclease (Cas). The sgRNA and Cas9 are combined into a ribonucleoprotein complex when they are used in CRISPR experiments.

• Cas9: It is an endonuclease enzyme which functions as a pair of molecular scissors to cut the target DNA sequence.
• sgRNA: Single-guide RNA is the combination of tracrRNA and crRNA. crRNA contains two main parts, the spacer sequence that directs the complex to the target DNA and a region that binds to tracrRNA. When tracrRNA binds to crRNA, a functional guide RNA is formed for Cas9 to recognize. Multiple crRNAs can be incorporated into a crRNA array and then packaged with tracrRNA to form a sgRNA.