Question: what are the substrate of nucleases?
Answer: RGENs are composed of a guide RNA and the Cas9 nuclease. This programmable nuclease is derived from an adaptive immune system in bacteria and archaea called the clustered, regularly interspaced, short palindromic repeat (CRISPR) system (Barrangou et al., 2007; Makarova, Grishin, Shabalina, Wolf, & Koonin, 2006).