Diagram the mechanism by which CRISPR–Cas functions in the immune system of bacteria and archaea.

Key Concepts

CRISPR-Cas System

The CRISPR-Cas system is a bacterial and archaeal adaptive immune mechanism that protects against viral infections. It consists of CRISPR sequences, which are segments of DNA containing short, repetitive sequences derived from past viral infections, and Cas proteins, which are enzymes that facilitate the targeting and destruction of foreign DNA. This system allows organisms to 'remember' past invaders and mount a rapid response upon subsequent infections.

Guide RNA

Guide RNA (gRNA) is a crucial component of the CRISPR-Cas system, serving as a template that directs the Cas proteins to the specific DNA sequence of the invading virus. The gRNA is complementary to the target DNA, allowing for precise binding and cleavage. This specificity is essential for the system's effectiveness, ensuring that only the intended viral DNA is targeted while leaving the host's genome intact.

DNA Cleavage

DNA cleavage is the process by which the Cas proteins, guided by the gRNA, cut the target viral DNA at specific sites. This action prevents the virus from replicating and spreading within the host. The cleavage typically occurs through the action of Cas9 or other Cas proteins, which introduce double-strand breaks in the viral DNA, leading to its degradation and effectively neutralizing the threat.