Okay, I haven't used crispr/cas9 in a couple years so I'm starting to get confused as I look over my old notes and the new literature (and the plasmids on AddGene!). I thought gRNA was a synthetic combination of tracrRNA and crRNA. However, I've seen plasmids with tracrRNA and gRNA (e.g. pMAZ-5k) and others with crRNA and gRNA (e.g. pFG001). Can't you just put the gRNA on the plasmid without the tracrRNA and crRNA? I'm also wondering if adding the tracrRNA when the gRNA is already present will 'compete' with the gRNA for binding to cas9. In the sense that the tracrRNA will put the cas9 in an active conformation state, ostensibly waiting for a crRNA (if this was a wild-type cell with a native cas9 system).

If anyone more experienced with crispr/cas9 can clarify this I'd appreciate it!