John Cairns called “the Meselson-Stahl experiment“, published in 1958, “the most beautiful experiment in biology.” (Click on the first screenshot below to see the original paper, but what I really want you to do is watch the video at the bottom).
The paper was by Matt Meselson, who became a Harvard professor and distinguished researcher, and Frank Stahl, who was equally distinguished and worked at The University of Oregon. Both men are now 91, and both are still with us. The videographers shot both men together, 63 years later, to discuss this most important work, one that, in an unbelievably simple and clever experiment, revealed how DNA replicated. (There were several theories about how the genetic material was duplicated.) I always thought they should have won the Nobel Prize for this experiment, but it was not to be.
A bit of backstory: on p. 166 of Horace Freeland Judson’s wonderful book about molecular biology, The Eighth Day of Creation, you can read this:
Soon after Meselson got back to Pasadena that winter, Max Delbrück and his wife carried [Meselson] and Stahl to the Kerkhoff Marine Station, run by Caltech, on the sea at Corona del Mar, and locked them into an upstairs room with two sleeping bags and a typewriter until they wrote the paper.
You can read the Wikipedia link to the experiment, but first watch the video at the bottom first, which explains this lovely bit of experimental molecular genetics. It’s a really wonderful view of two aging scientists remembering their greatest moment.
This video truly conveys the excitement of the early days of molecular genetics in the 1950s after Watson and Crick had published their proposed structure. W&C had suggested a method of replication of DNA, but it wasn’t really “proven” until the Meselson/Stahl experiment.
. At the end, the two collaborators and friends visit the llamas that Stahl now farms