In the 1958 Meselson–Stahl experiment, what model of DNA replication did the results support?

The 1958 Meselson–Stahl experiment supported semiconservative replication of DNA.

Matthew Meselson and Franklin Stahl grew E. coli in a medium containing heavy nitrogen-15, then moved the bacteria to ordinary nitrogen-14. They separated DNA by density-gradient centrifugation after each generation. DNA made after one generation formed an intermediate-density band, showing that each molecule contained one old heavy strand and one new light strand.

After two generations, the DNA produced both intermediate and light bands. This result ruled out the conservative model, which predicted separate all-heavy and all-light molecules after the first generation. It also ruled out the dispersive model, which predicted progressively mixed strands.

The experiment confirmed a prediction made by James Watson and Francis Crick in 1953. Semiconservative replication means that the two strands of a DNA molecule separate, and each serves as a template for a new complementary strand.