Scientists are finding ways to manipulate the Cas9 protein for improved genome editing. Identify all of the following four reasons why scientists may generate mutations in the HNH or RuvC endonuclease domains of Cas9: 1) Generation of a Cas9 nickase 2) Production of dCas9 3) Increased binding specificity of Cas9 to target DNA 4) Promotion of non-homologous end joining