Restriction enzymes are used in genetic engineering to cut DNA at specific sequences, producing ends that can be joined.

• A. They transport plasmids across membranes.
• B. They synthesize DNA strands de novo.
• C. They cut DNA at specific sequences to produce ends that can be joined.
• D. They translate RNA into proteins.

Answer: (C)

Restriction enzymes act as molecular scissors that recognize specific DNA sequences and cut at those sites. This creates DNA fragments with defined ends—sticky ends or blunt ends—that can be joined to other DNA fragments, such as a plasmid vector, using DNA ligase to form a recombinant molecule. This precise cutting and joining is the fundamental tool in genetic engineering for cloning genes and constructing new DNA combinations. The other activities described—transporting DNA across membranes, synthesizing DNA strands de novo, and translating RNA into proteins—are not functions of restriction enzymes.