For the pARA-R plasmid used in cloning experiments, how many restriction sites are present for the enzymes used?

For the pARA-R plasmid used in cloning experiments, how many restriction sites are present for the enzymes used?

• A. One
• B. Three
• C. Four
• D. Two

Answer: (D)

Restriction sites on a plasmid determine where a DNA fragment can be inserted and, when using two different enzymes, help ensure the insert goes in with a defined orientation. For the pARA-R plasmid used in these experiments, there are two sites for the enzymes being used. Digesting with those two enzymes creates a single cloning window between the sites, producing ends that match the insert prepared with the same enzymes. This enables directional cloning, so the insert ligates in the correct orientation rather than in the wrong direction. If there were only one site, orientation would be ambiguous; if there were more than two sites, multiple cutting locations could complicate cloning and increase unwanted fragments.

Restriction sites on a plasmid determine where a DNA fragment can be inserted and, when using two different enzymes, help ensure the insert goes in with a defined orientation. For the pARA-R plasmid used in these experiments, there are two sites for the enzymes being used. Digesting with those two enzymes creates a single cloning window between the sites, producing ends that match the insert prepared with the same enzymes. This enables directional cloning, so the insert ligates in the correct orientation rather than in the wrong direction. If there were only one site, orientation would be ambiguous; if there were more than two sites, multiple cutting locations could complicate cloning and increase unwanted fragments.