Figure 1.

Mechanism of immunity against virus invaders through CRISPR-Cas systems. The molecular defense process of the CRISPR-Cas system includes three phases: adaptation, maturation, and interference. Adaptation: the host organism captures the nucleotide fragments from invaders and integrates them into the CRISPR array; Maturation: CRISPR array is transcribed into precursor crRNA (pre-crRNA) and further processed into mature crRNA; Interference: crRNA binds to the effector Cas protein to form a complex, and the target invader genome (DNA/RNA) is identified and bound with the help of crRNA, which eventually leads to the degradation of the invader genome (DNA/RNA).