The banding patterns of the DNA fragments in the Meselson-Stahl experiment reveal that:

• A. DNA replication is dispersive, with each strand being a mix of old and new DNA segments.
• B. DNA replication is conservative, with one molecule containing both old strands and the other both new strands.
• C. DNA replication is semiconservative, with each daughter molecule containing one old and one new strand.
• D. DNA fragments are identical in density regardless of replication method.

Answer: (C)

Verified step by step guidance

1. Understand the Meselson-Stahl experiment setup: They grew bacteria in a heavy isotope of nitrogen (\(^{15}N\)) and then shifted them to a lighter isotope (\(^{14}N\)) to track DNA replication over generations.
2. Recognize that DNA replication models predict different distributions of DNA densities after replication: conservative replication predicts separate heavy and light DNA molecules; semiconservative predicts hybrid molecules with one old and one new strand; dispersive predicts mixed strands throughout each molecule.
3. Analyze the banding patterns observed after centrifugation: after one round of replication, a single intermediate density band appears, which rules out conservative replication because no separate heavy band remains.
4. After subsequent rounds, observe the appearance of both light and intermediate bands, which is inconsistent with dispersive replication that would produce only intermediate density bands.
5. Conclude that the pattern of one intermediate band after the first replication and both intermediate and light bands after further replications supports the semiconservative model, where each daughter DNA molecule contains one old and one new strand.