The components of the CRISPR system are the Cas9 endonuclease, and a single-guide RNA (sgRNA). Within the Cas9 protein are two nuclease domains, RuvC and HNH. Each is responsible for cleaving one strand of the target double-stranded DNA. An sgRNA simplifies the process of the CRISPR system by combining the functions of both crRNA and tracrRNA into a single molecule. crRNA binds to foreign DNA and the trans-activating CRISPR RNA (tracrRNA) hybridizes with it. The sgRNA and Cas9 nuclease combine to create a Cas9 ribonucleoprotein (RNP) that can recognize and cut the desired DNA target.