Interview with David Baltimore - Caltech Oral Histories

Baltimore-12
BALTIMORE: Yes. That experiment showed that when DNA duplicates, you open the helix and
you duplicate the individual strands. There’s a whole book about that experiment, which was
published by this wonderful historian of science at Yale who died a few years ago, called The
Greatest Experiment, or something like that. 2 And many people considered it the greatest
experiment. When I invited a great geneticist, George Streisinger, to come to Swarthmore—I
was the head of a little biology club and I invited George to come and give a lecture, because I’d
worked with him at Cold Spring Harbor—George came and said, “I don’t want to talk about my
own work. The greatest experiment in biology has been done just recently, by Meselson and
Stahl, and I want to explain that experiment.” And he got up to the board and just simply spent
an hour explaining that experiment.
LIPPINCOTT: So what they showed was what—
BALTIMORE: The big question was, If the helix is in fact wound around itself, the information is
at the center—because the information is the base pairs. How do you get at the information
And the notion that you can take apart a chemical—
LIPPINCOTT: That it unzips
BALTIMORE: That it unzips—was very hard for people to accept. Now, Watson and Crick
accepted it very easily.
LIPPINCOTT: They saw it.
BALTIMORE: They saw it and they made a picture of it, but there was no experimental
verification that the helix came apart. You know, in the history of science it’s interesting how
experiments that are not necessarily the most insightful somehow strike the community as the
thing they want to know. If they know that, then they accept a whole realm of theory around it.
And the Meselson-Stahl experiment was that. It gave people the courage to believe that the ’53
paper had it right.
2 Frederic Lawrence Holmes, Meselson, Stahl, and the Replication of DNA: A History of “The Most Beautiful
Experiment in Biology” (New Haven: Yale University Press, 2001).