Meselson–Stahl experiment

[1] Meselson and Stahl decided the best way to trace the parent DNA would be to tag them by changing one of its atoms.

In the semiconservative hypothesis, proposed by Watson and Crick, the two strands of a DNA molecule separate during replication.

According to this model, histone proteins bind to the DNA, revolving the strand and exposing the nucleotide bases (which normally line the interior) for hydrogen bonding.

[3] The dispersive hypothesis is exemplified by a model proposed by Max Delbrück, which attempts to solve the problem of unwinding the two strands of the double helix by a mechanism that breaks the DNA backbone every 10 nucleotides or so, untwists the molecule, and attaches the old strand to the end of the newly synthesized one.

[4] Each of these three models makes a different prediction about the distribution of the "old" DNA in molecules formed after replication.

The dispersive model predicts that each strand of each new molecule will contain a mixture of old and new DNA.