Which enzyme cuts DNA at specific sequences, a key tool in genetic manipulation?

• A. Ligase
• B. Nuclease
• C. Reverse Transcriptase
• D. Restriction enzyme

Answer: (D)

Restriction enzymes cut DNA at specific sequences, which is essential for precise genetic manipulation. They recognize short, defined DNA motifs and cleave at those sites, providing predictable, site-specific breaks. This allows scientists to excise a gene of interest and insert it into a vector, or to assemble DNA fragments with compatible ends before sealing them with ligase. The other enzymes have different roles: ligase joins DNA ends, reverse transcriptase makes DNA from RNA, and nucleases can cut DNA in a non-specific or general way. The hallmark of restriction enzymes is their ability to target a particular DNA sequence and cut there, enabling controlled genetic engineering.