E-Mail IMAGE: Left - a schematic of the long form of the tracrRNA used by the CRISPR-Cas9 system in bacteria; Right - the standard guide RNA used by many scientists as part... view more Credit: Joshua Modell, Rachael Workman and Johns Hopkins Medicine In a series of experiments with laboratory-cultured bacteria, Johns Hopkins scientists have found evidence that there is a second role for the widely used gene-cutting system CRISPR-Cas9 -- as a genetic dimmer switch for CRISPR-Cas9 genes. Its role of dialing down or dimming CRISPR-Cas9 activity may help scientists develop new ways to genetically engineer cells for research purposes.