A centrifuge was used to separate DNA molecules labeled with isotopes of different densities. This experiment revealed a pattern that supports the semiconservative model of DNA replication.

So why didn't Meselson and Stahl finally explain this mechanism until 1958? Semiconservative replication was not the only model of DNA replication proposed during the mid-1950s, however.

Matthew Meselson and Franklin Stahl's 1957 demonstration of DNA replication is considered "the most beautiful experiment in biology." Their density-shift demonstrations not only have stood the test of ...