Question

Which enzyme protects host DNA from restriction digestion?

• A. DNA ligase
• B. Restriction endonuclease
• C. DNA methyltransferase
• D. DNA polymerase

Hint:

Restriction-modification system: \[ \boxed{ \begin{aligned} \text{Restriction enzyme} &\rightarrow \text{Cuts foreign DNA} \text{DNA methyltransferase} &\rightarrow \text{Protects host DNA} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Recall the restriction-modification system. Bacteria possess restriction enzymes that cleave foreign DNA and methyltransferases that methylate their own DNA.

Step 2: Identify the protective enzyme. DNA methyltransferase modifies specific recognition sites on host DNA, preventing restriction endonucleases from cutting it. Thus, \[ \boxed{\text{DNA methyltransferase}} \] protects host DNA. Therefore, \[ \boxed{(C)} \] is the correct answer.