What is the purpose of restriction enzymes in cloning?

• A. To replicate DNA.
• B. To cut DNA at specific sequences, enabling gene splicing and recombinant DNA creation.
• C. To ligate DNA fragments together.
• D. To transcribe RNA from DNA.

Answer: (C)

Restriction enzymes cut DNA at specific sequences, producing fragments with defined ends. This is the essential first step in cloning: you slice out a gene of interest and open a vector so the gene can be inserted. The ends on the gene fragment and the vector can be made compatible, allowing them to be joined to form recombinant DNA. The actual joining is done by DNA ligase, while the cuts themselves are what enable the gene splicing that creates new DNA combinations. Replication, transcription, and ligation are carried out by other enzymes (DNA polymerase, RNA polymerase, and DNA ligase, respectively), not the restriction enzymes.