Question

Originally, restriction endonucleases (REN) are named so because they __________

• A. restrict DNA replication in host bacterium.
• B. cut the DNA strands at specific restriction site.
• C. destroy viral DNA to restrict the potential growth of virus in bacteria.
• D. restrict the translocation of viral DNA to prevent viral protein formation.

Hint:

The name comes from the bacterial defence role: they limit (restrict) virus growth in the host bacterium.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
Restriction endonucleases were discovered as defence enzymes of bacteria.

Step 2: How they defend
When a bacteriophage infects a bacterium, these enzymes cut the foreign viral DNA. The bacterium's own DNA is protected by methylation.

Step 3: Origin of the name
By destroying viral DNA they restrict the multiplication of the virus in the host. This is why they were named restriction enzymes. Cutting at specific sites describes how they work, not the reason for the name.

Final Answer:
They were named so because they destroy viral DNA and restrict virus growth in bacteria. \[ \boxed{\text{(C) }\text{destroy viral DNA to restrict the potential growth of virus in bacteria}} \]