Which gene-editing system uses guide RNA and the Cas9 protein to cut DNA?

CRISPR-Cas9 is a gene-editing system that uses guide RNA and the Cas9 protein to cut DNA.

The guide RNA contains a sequence designed to pair with a chosen DNA target. Cas9 then makes a double-strand break near that target, provided the surrounding DNA includes an appropriate protospacer-adjacent motif. The cell's repair pathways can create small changes or, with a supplied template, introduce a planned sequence.

CRISPR systems originated as bacterial and archaeal defence mechanisms against genetic material from viruses. Researchers adapted them into programmable tools after work involving scientists including Jennifer Doudna and Emmanuelle Charpentier, who shared the 2020 Nobel Prize in Chemistry.

CRISPR-Cas9 is powerful but not automatically perfect. Unintended edits, delivery challenges and ethical questions remain important considerations. It is also different from RNA interference, which usually reduces gene expression without cutting genomic DNA.