DNA Structure and Bonding

Steps:

• Recall DNA's double helix consists of two antiparallel strands with complementary base pairing.
• Identify backbone formation: nucleotides link via phosphodiester bonds between sugar and phosphate.
• Note enzymes involved: DNA polymerase synthesizes most bonds, but DNA ligase seals nicks in replication.
• Evaluate each option against standard DNA features.

Why C is correct:

• Phosphodiester bonds form the sugar-phosphate backbone; DNA ligase catalyzes their formation during replication by joining Okazaki fragments (per molecular biology definition of ligation).

Why the others are wrong:

• A: Strands are antiparallel, not parallel.
• B: A-T pairs have two hydrogen bonds; only G-C has three.
• D: Backbone consists of phosphate-sugar alternating units, not "phosphate molecules and nucleotides" (nucleotides are the full monomers).

Final answer: C