Final answer:
Meselson and Stahl's experiment concluded that DNA replication is semi-conservative. The hypothetical results mentioned in the question do not specify any particular outcome, therefore, we cannot determine which replication model they support without additional data. Option b is the correct answer.
Step-by-step explanation:
The student has asked a question about the results of Meselson and Stahl's famous experiment on DNA replication, which tested three models: conservative, semi-conservative, and dispersive. However, the question presents a hypothetical scenario without specific results. Without clear data, we cannot definitively state which model of replication these hypothetical results support.
Meselson and Stahl's actual experiment used isotopes of nitrogen to label the DNA and distinguished between these models by centrifugation and density gradient analysis. After one round of replication, they observed an intermediate band of DNA, ruling out the conservative model. After a second round of replication, two distinct bands were observed: one intermediate and one light, which dismissed the dispersive model and supported the semi-conservative model. This outcome demonstrated that DNA replication is semi-conservative, meaning each new DNA molecule consists of one old and one new strand.
If Meselson and Stahl had obtained a result showing two bands after the first generation, it would have suggested the conservative model of replication. But their actual experiment showed that DNA replication was not conservative but semi-conservative, thus confirming that each new DNA molecule contains one strand from the original molecule and one newly synthesized strand.