THE DISCOVERERS OF THE CRISPR/CAS9 METHOD,
Emmanuelle Charpentier and Jennifer Doudna,
copied a defensive trick they observed in bacteria for this technology. When bacteria are attacked by viruses, they save a part of the attacker’s DNA—like a type of “mug shot” known as gRNA—in a database: its CRISPR genetic sequence (clustered regularly interspaced short palindromic repeats). If they are later attacked by the same virus again, the bacteria send out Cas9 proteins that identify the enemy DNA using the saved mug shot and destroy it by carving up its genome.