Question

The enzyme that makes a cut at a specific position within the DNA is called:

• A. Exonuclease
• B. Endonuclease
• C. Ligase
• D. Polymerase

Hint:

Remember 'endo' means inside; this enzyme cuts inside the DNA molecule, not at its ends.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Genetic engineering needs a tool that cuts DNA at one exact, recognisable sequence rather than chopping it randomly from the ends. That tool is a restriction endonuclease.

Step 2: Recall how it works.
A restriction endonuclease scans the DNA strand, finds its specific short recognition sequence, and cuts the sugar-phosphate backbone right at (or near) that internal site, inside the molecule.

Step 3: Why the other options are wrong.
An exonuclease removes nucleotides one at a time from the free ends of DNA, not from an internal site. Ligase does the opposite job, it joins (seals) two DNA fragments together. Polymerase builds a new DNA strand by adding nucleotides; it does not cut DNA.

Final Answer:
The enzyme that cuts DNA at a specific internal site is the endonuclease, option (B).