What is used to cut DNA into fragments for analysis or cloning?

• A. Polymerase
• B. Ligase
• C. Restriction enzyme
• D. Nuclease

Answer: (C)

Restriction enzymes cut DNA at specific sequences, producing defined fragments. This sequence-specific cleavage is what makes them indispensable for both analysis and cloning: you can predict the fragment sizes, separate them by gel electrophoresis, map pieces of DNA, or insert fragments into vectors with compatible ends. Some restriction enzymes leave sticky ends with overhangs that help fragments find and pair with each other, while others create blunt ends.

In contrast, polymerase builds new DNA strands, ligase joins together DNA fragments after they’ve been cut, and nucleases broadly degrade nucleic acids. None of those provide the precise, predictable cutting pattern needed to generate fragments for mapping or cloning in the same way restriction enzymes do.