Semi-Conservative DNA Replication

Steps:

• DNA replication follows the semi-conservative model, where each parental strand pairs with a new strand.
• After unwinding, the original double helix produces two daughter molecules.
• Each daughter molecule contains one intact parental strand and one newly synthesized strand.
• The correct diagram shows two hybrid DNA duplexes.

Why C is correct:

• It illustrates two DNA molecules, each with one parental (old) strand and one daughter (new) strand, matching the semi-conservative replication mechanism established by the Watson-Crick model and confirmed by the Meselson-Stahl experiment.

Why the others are wrong:

• A shows conservative replication, with parental strands remaining together and new strands forming a separate duplex.
• B depicts dispersive replication, with old and new segments mixed randomly in both strands.
• D shows both strands fully new in daughter molecules, violating template-directed synthesis.

Final answer: C