Recorded: 14 Jul 2000
The question was right—how does it all work? Who reads this and how is it read? And perhaps most important, in this was a thing that had worried people for years: how do you have a message that can be copied and who is wise enough to be able to copy this? After all, you invent a Xerox machine but the inventor of the Xerox machine has to be much cleverer than the piece of paper that he’s Xeroxing. So, how was this done?
Well, there were two discoveries in 1957 that resolved that problem most beautifully. The first and simplest discovery in the sense of understanding, what it was about, was a discovery by Arthur Kornberg of an enzyme that given bits of DNA would proceed to copy it in a completely mindless and precise way. And obviously [since] the message in DNA which is enormously long—only tiny little bits of this message are needed to code the enzyme but [it] copies the whole thing. So here you got rid of one of the problems that had deviled people over the years.
The other problem was: okay, how does it copy DNA? You’ve got two strands, which are inexplicably linked. How does it make two double-stranded molecules where before there was only one? One of the possibilities was that it actually unwinds the strands and makes a copy alongside each one, so that you have, as it were, a fork where the two strands come apart and each one is copied. And the Meselson/Stahl density transfer experiment was the experiment that showed that that is exactly how DNA is copied and the details are in any book.
But it’s a very elegant experiment—and was actually going on and was the burning topic of conversation at mealtime. So actually I was the oldest member of the house so the younger ones talked about girls and the density transfer experiment. I talked about the density transfer experiment and washing up—which was my specialty!
John Cairns, physician and molecular biologist, received his degree in medicine from Oxford University in 1946. Cairns worked as a virologist at the Walter and Eliza Hall Institute in Melbourne, at the Virus Research Institute in Entrebbe, Uganda and at the Curtain School of Medical Research in Canberra.
From 1960-61, Cairns spent his sabbatical at Cold Spring Harbor Laboratory under Alfred Hershey. He returned to serve as director of the Lab from 1963-1968, while continuing his research on DNA replication and initiating the technique autoradiography. During Cairns’s tenure, he saw Cold Spring Harbor Laboratory officially form from an amalgamation of the Long Island Biological Association’s Biological Laboratory and the Carnegie Institution of Washington’s Department of Genetics. Cairns remained a staff member until 1972 when he was appointed head of the Mill Hill Laboratory of the Imperial Cancer Research Fund. Cairns subsequently worked at the Harvard School of Public Health until his retirement in 1991.
In addition to Cairns’s scientific endevours, he is also one of the editors of Phage and the Origins of Molecular Biology.