Final answer:
DNA replicates following the semi-conservative model, where each new DNA molecule consists of one strand from the parent molecule and one new strand. This was conclusively demonstrated by Meselson and Stahl's experiments using isotopes of nitrogen to differentiate between old and new DNA strands.
Step-by-step explanation:
The correct model by which DNA replicates is semi-conservative. This was confirmed through the famous experiments conducted by Matthew Meselson and Franklin Stahl. In the semi-conservative model of DNA replication, the two strands of the parental DNA helix separate, and each acts as a template for the synthesis of a new, complementary strand. After replication, each DNA molecule consists of one parental strand and one newly synthesized strand. This contrasts with the conservative model, where the original DNA molecule is fully conserved and a completely new molecule is synthesized, and the dispersive model, where the strands are a mixture of old and new DNA.
The evidence supporting the semi-conservative model was gathered using experiments that labeled the DNA with different isotopes of nitrogen, allowing the researchers to distinguish between old and new strands of DNA after the replication process. These experiments established that every new DNA molecule contains one old (parental) strand and one new strand, which was indicative of semi-conservative replication.