Cas9 is an endonuclease enzyme that plays a crucial role in the immune defense mechanism of bacteria and archaea. It is used by these microorganisms to cut the DNA of invading viruses, thus neutralizing the threat. The enzyme is guided to its target DNA by a piece of RNA called guide RNA (gRNA). This specificity makes Cas9 a valuable tool for gene editing, as it can be programmed to target specific DNA sequences in various organisms.
