Figure 1 -. Adaptive immunity by CRISPR-Cas systems.
a) Foreign genetic elements are acquired by Cas1/Cas2 and integrated into the CRISPR-array in a process broadly termed adaptation. b) The CRISPR array and associated Cas proteins are expressed. The CRISPR array is processed and Cas effector nucleases associate with a crRNA to form an active surveillance complex. c) The Cas effector nucleases target foreign genetic elements complementary to their crRNA leading to target interference and immunity.