Table 1.

The classification of CRISPR/Cas systems.

		Effector Module	Pre-crRNA Processing	Interference Stage (Target Cleavage)
Class 1	Type I	Multi-subunit effector complex	Cas6	Cas3
	Type III			Subunit of the processing complex
	Type IV			Uncharacterized
Class 2	Type II	Single multi-domain protein	RNase III	Nuclease domain of the effector protein
	Type V		Nuclease domain of the effector protein
	Type VI