Question

Bacteria uses restriction endonuclease to protect itself from viral attack. The bacterial DNA does not get degraded by its own enzyme because

• A. DNA of bacteria is able to reintegrate itself.
• B. Bacterial DNA does not have specific site.
• C. Bacterial DNA protect itself by changing the configuration of active site.
• D. The enzyme cannot identify the sites.

Answer 1

The correct option is C Bacterial DNA protect itself by changing the configuration of active site.

Bacteria have restriction endonucleases, which cleave double stranded DNA at specific points. This prevents viral infection of by destroying the viral DNA introduced by a bacteriophage. Therefore, in order to prevent the destruction of its own DNA by the restriction enzymes, bacteria uses modification system where they modify their DNA by adding methyl groups. This modification must not interfere with the DNA base-pairing, and therefore, usually only a few specific bases are modified on each strand.

Thus, the correct answer is option C.