Question

Which step in recombinant DNA technology prevents self-ligation of vector DNA during gene cloning?

• A. Digestion of vector and insert with the same restriction enzyme
• B. Treatment of vector DNA with DNA ligase
• C. Dephosphorylation of vector DNA using alkaline phosphatase
• D. Using a selectable marker in the vector

Answer 1

Answer:

C. Dephosphorylation of vector DNA using alkaline phosphatase

• Alkaline phosphatase removes 5' phosphate groups from linearized vector ends, preventing DNA ligase from joining them (self-ligation). The insert retains phosphates for successful ligation.