複選題22. The 2020 Nobel Prize in Chemistry was awarded for the discovery of CRISPR. Which of the following descriptions of CRISPR is (are) CORRECT? (A) CRISPR is a bacterial immune system used to defend against bacteriophages. (B) The targeted DNA cleavage of CRISPR systems from different bacteria involves one RNA and one Cas protein. (C) The major breakthrough in CRISPR research was its efficient targeted DNA cleavage at any given position, provided a PAM sequence is present. (D) CRISPR can only be used for targeted DNA cleavage. (E) The CRISPR system in bacteria recognizes bacteriophages by incorporating parts of their DNA sequences into the bacterial genome.