The Cas9::CMP(Unk) entry in FlyBase represents a fusion protein in which a Cas9 RNA-guided nuclease (derived from the naturally occurring Cas9 endonuclease from Streptococcus pyogenes and in which the two nuclease domains present in the naturally occurring protein are functional) is fused to one or more chromatin-modulating peptides (CMPs), but the origin of one or more of the CMPs is unknown or not specified. The presence of the CMPs is expected to increase the activity of Cas9::CMP(Unk) compared to unmodified Cas9, particularly on refractory target sites.