[Campbell Biology P.410] What is the primary function of the Cas9 protein's active sites in ... | Practice Question

What is the primary function of the Cas9 protein's active sites in the CRISPR-Cas9 system as depicted in Figure 17.28, and what are the two possible outcomes for the broken DNA strands?

  • A: The active sites synthesize new DNA strands; the broken strands are always repaired to be functional.
  • B: The active sites bind to the target gene; the broken strands can either be knocked out or synthesized into a correct sequence.
  • C: The active sites cut the DNA on both strands; the broken strands can either be made nonfunctional by random nucleotide insertion/deletion or repaired using a normal gene template.
  • D: The active sites guide the RNA to the target gene; the broken strands are immediately discarded by the cell.

Explanation

As shown in Figure 17.28, the Cas9 protein's active sites are explicitly stated to 'cut DNA' Step 1 and 2 . Step 3 details two repair pathways for the broken DNA strands: one where random nucleotides are inserted/deleted, making the gene nonfunctional knockout , and another where a normal gene copy is used as a template to synthesize the correct gene sequence repair of mutation .