CRISPR stands for “clustered regularly interspaced short palindromic repeats”, which are usually found in the DNA of bacteria. These repeats are in fact snippets of DNA that the bacteria capture from invading viruses. Bacteria collect these snippets as mug shots to help them remember the viruses. If the virus attacks again, the bacteria identifies it from its mug shot collection and fights it off by sending the Cas9 enzyme to cut the DNA apart and disable the virus. Cas9 is a special type of enzyme that is capable of cutting apart DNA on order. The DNA segments that are created are known as CRISR arrays.

he CRISPR immune system works to protect bacteria from repeated viral attack via three basic steps:

• Adaptation: DNA from an invading virus is processed into short segments that are inserted into the CRISPR sequence as new spacers.
• Production of CRISPR RNA – CRISPR repeats and spacers in the bacterial DNA undergo transcription, the process of copying DNA into RNA (ribonucleic acid).
• Targeting: CRISPR RNAs guide bacterial molecular machinery to destroy the viral material.