A conceptual illustration of genome editing using clustered regularly interspaced short palindromic repeats (CRISPR). In order to edit a genetic sequence, a Cas9 protein (purple) attaches to the DNA of a cell using a guide RNA (orange) that matches a target DNA sequence, and separates the double helix. A protospacer adjacent motif (PAM) sequence on the cell's DNA (green) indicates where the Cas9 protein locks down and "cuts" the target DNA. Once the sequence has been cut, the DNA can be disabled or altered.