FIGURE 1.

Adaptive immune response in the CRISPR-Cas system. This figure was drawn by Figdraw. (A) In the adaption stage, some short fragments of viruses, plasmids and other foreign nucleic acids are integrated into CRISPR repeats to form spacer sequences. (B) In the expression stage, CRISPR sequences were processed into crRNA containing spacer and repeat sequences, which were combined with CRISPR-associated effector proteins to form complexes. (C): In the interference stage, the complex performs specific cleavage and inactivation of foreign nucleic acids complementary with crRNA sequences, so as to protect itself from viruses, plasmids and other invasion.