Semi-conservative DNA replication

Steps:

• DNA double helix unwinds, separating into two single strands.
• Each original strand acts as a template for synthesizing a complementary new strand via base pairing.
• DNA polymerase adds nucleotides to the growing new strands in 5' to 3' direction.
• Two daughter molecules form, each with one original and one new strand.

Why C is correct:

• Diagram C depicts the two original strands separating, with each templating a new complementary strand, aligning with the semi-conservative replication model established by Meselson-Stahl experiment.

Why the others are wrong:

• A: Shows synthesis of an entirely new double helix without incorporating original strands, violating template usage.
• B: Illustrates both new strands forming simultaneously on one template, ignoring bidirectional replication.
• D: Depicts the original double helix remaining intact while a new one forms separately, representing conservative replication.

Final answer: C