CRISPR-Cas9 gene editing: Check three times, cut once

CRISPR-Cas9 is a powerful tool to edit genomes, but off-target edits are a concern. Now studies detail three checks the Cas9 protein makes to ensure it binds the right DNA and that the sequence matches the RNA primer sufficiently to warrant cutting. At most off-target sites, Cas9 binds for milliseconds. Once it sticks for about a minute, two distant regions of the protein come together like the blades of a scissors to trigger cutting.