How does CRISPR-Cas9 specifically target and edit genes in an organism?

CRISPR‑Cas9 works by first using a short RNA sequence that is designed to match a specific gene in the genome; this RNA acts like a GPS that tells the Cas9 protein where to go. When the guide RNA finds its matching DNA, Cas9 binds and makes a clean cut in the DNA strand at that exact spot. The cell then repairs the break, and scientists can add, delete, or replace the DNA at that location, creating a precise edit. For example, a guide RNA can target the sickle‑cell mutation in the hemoglobin gene, and after Cas9 cuts, the cell can be instructed to insert a healthy version of the gene so the patient’s red blood cells no longer produce the faulty protein.