Some bacteria possess a fascinating system for combatting viral infections called CRISPR (Clustered Regularly Interspersed Short Palindromic Repeats).
The spacer DNAs are actually sequences from viral genomes, that were copied and placed between the palindromic repeats during a viral infection. Through the action of the Cas enzymes, the viral sequences can be used to target viral RNA or DNA for destruction. DNA sequences from different viruses are retained and can be used as a defense against the viruses in the future.
A. Which steps in the CRISPR mechanism are most similar to the Dicer and RISC steps of the iRNA process of eukaryotes?
B. Describe three similarities between the functions or mechanisms of the RNAi and the CRISPR. (e.g., â€œ In both CRISPR and iRNAâ€¦â€)
C. Other than the specific enzymes involved, identify three differences between the RNAi and the CRISPRmechanisms. (e.g., â€œ In CRISPR â€¦, whereas in iRNAâ€¦â€)
D. Explain the function of the palindromic repeats in the CISPR mechanism?