What term describes the pairing of complementary DNA strands to form the double helix?

• A. Hybridize
• B. Anneal
• C. Pairing
• D. Ligation

Answer: (B)

Annealing describes the pairing of complementary DNA strands to re-form the double helix, driven by specific base pairing through hydrogen bonds between A–T and G–C. After strands are separated (denatured) by heat, cooling allows them to find their partners and reassemble into a stable duplex, which is the annealing step you often see in PCR and related techniques. While hybridize can refer to binding of nucleic acids in a broader sense, annealing emphasizes the reformation of the correct duplex through precise base pairing. Ligation is the enzymatic joining of DNA fragments, and pairing is too general to capture the specific, base-pair–driven duplex formation.