The structure of DNA

Host: Kerri Smith

This is the Nature PastCast, each month raiding Nature’s archive and looking at key moments in science. In this show, we’re going back to the 1950s.

Music: I’ve Got the World on a String by Ella Fitzgerald

Voice of Nature: John Howe

From the Editorial and Publishing Offices of Nature, Macmillan and Co., St Martin’s Street, London. Nature, April 25^th 1953.

Music: I’ve Got the World on a String by Ella Fitzgerald

Voice of Nature: John Howe

Page 734, Microsomal particles of normal cow’s milk. Page 737, Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid, J. D. Watson and F. H. C. Crick.

Music: I’ve Got the World on a String by Ella Fitzgerald

Raymond Gosling

Walking into the lab and seeing this double helix, of course, it looked familiar because all of the stator of the dimensions was the stuff that we got from our X-ray diffraction patterns. So, it looked right and it was sheer elegance.

Music: I’ve Got the World on a String by Ella Fitzgerald

Raymond Gosling

I’m Raymond Gosling, co-author of one of the papers in Nature, 1953, April, on the structure of DNA.

Music: I’ve Got the World on a String by Ella Fitzgerald

Melinda Baldwin

My name is Melinda Baldwin. I’m a historian of science at the American Academy of Arts and Sciences in Cambridge, Massachusetts. I think a lot of people don’t necessarily know that there were three DNA papers instead of just the one, and I think the big reason that the Watson and Crick paper became the one that we do remember is because that’s the one where the structure of DNA was published, and I think as a consequence the second two papers have really fallen out a bit of consciousness. The Franklin and Gosling paper was primarily about crystallographic work.

Voice of Nature: John Howe

Page 740, Rosalind E. Franklin and R. G. Gosling, King’s College London, Molecular Configuration in Sodium Thymonucleate.

Georgina Ferry

I’m Georgina Ferry. I’m a science writer and author. At the time, X-ray crystallography of large molecules – the sort of molecules that you get in living bodies – was still a very, very small field. It had really started in the 1930s. Everybody was interested in the structure of proteins back in the 30s because nobody thought that DNA could possibly be complicated enough to be the molecule of life. That wasn’t really discovered until the mid-40s and then, obviously, it became very important to study its structure.

Raymond Gosling

The only time I could get at the X-ray set in King’s, the only one that existed, was in the basement of the chemistry department, and that was below the level of the Thames and I was only allowed to play with it in the evenings.

Georgina Ferry

What you need is an X-ray source, which in those days would have been an X-ray tube. I mean it was a form of technology that was available from the 19^th century but it’s a tube full of gas that you run an electric current through and it emits X-rays, and then in order to study your molecule, the thing you’re interested in, you have to crystallise it. You surround that, in the early days, with photographic film so that when the X-rays come in, they hit the atoms in the crystal and they’re diffracted out and they make spots on the photographic film.

Raymond Gosling

I needed lots of fibres. One would produce the diffraction pattern so weak that you’d never see it, so I wound 35 fibres round a paperclip and then pushed the clip open a bit to make the fibres taught.

Voice of Nature: John Howe

Sodium thymonucleate fibres give two distinct types of X-ray diagram. The first corresponds to a crystalline form, structure A. At higher humidities, a different structure, structure B, appears.

Raymond Gosling

And the best structure B pattern we ever got is photo 51, which I took and was called 51 because that was the 51^st photograph that we’d taken, Rosalind and I, in our efforts to sort out this A and B difference.

Melinda Baldwin

It’s a really beautiful photo. It’s very crisp, it’s very clean, it’s got this really neat ‘X’ shape, and apparently if you know something about crystallography, this photo just screams helix.

Georgina Ferry

What is puzzling, I think is still puzzling, is why they didn’t pursue that photograph once they had it.

Raymond Gosling

Now, Rosalind was absolutely determined that there was so much information in structure A’s diffraction pattern that was what she wanted to do and therefore put this photo 51 on one side and said we’ll come back to that. I only wish I’d been able to plug the value of looking at structure B as well as Structure A.

Ella Fitzgerald – I’ve Got the World on a String

Melinda Baldwin

So, Rosalind Franklin was working with Maurice Wilkins but the two of them had a pretty bad working relationship. Apparently, Franklin thought that she was being brought to King’s College London as an independent investigator who would be in charge of her own research. Wilkins thought that she was being brought in as an assistant, and eventually the relationship grew so fraught that Franklin stopped showing him her data, and she was planning on moving to Birkbeck College. Somehow, Wilkins got a copy of photo 51.

Raymond Gosling

I took it down the corridor and gave it to him because it had reached the stage now when Rosalind was going to leave, so she suggested that I go down the corridor and give this beautiful structure B pattern, this photo 51, to Maurice. Maurice couldn’t believe it when I offered it to him. He couldn’t believe that I hadn’t stolen it from her desk. He didn’t think that she could ever offer him something as interesting as this. He’d only had it for two or three days when Watson chipped up.

Melinda Baldwin

He showed it to James Watson when James came down to visit him and to chat a little bit about DNA.

Raymond Gosling

Who of course knew what a helical diffraction pattern would look like because Crick had two years previously published a theoretical paper of what the diffraction pattern of a helix would look like.

Melinda Baldwin

Watson’s got this great passage in The Double Helix where he said my pulse sped up and my heart began to race because he looked at this photo and realised immediately that DNA was helical and that he knew what size the turns had to be. So, this photo contained all of the information that he needed to build the model that he and Crick ended up being famous for.

Ella Fitzgerald – I’ve Got the World on a String

Voice of Nature: John Howe

We wish to suggest a structure for the salt of deoxyribose nucleic acid (D. N. A). This structure has two helical chains, each coiled round the same axis.

Georgina Ferry

So, it was pretty out of order for Watson and Crick to start working on DNA because they knew full well that Maurice Wilkins was working on it at King’s and subsequently Rosalind Franklin joined him there and she was also working on it. But it was King’s’ problem, and there was very much a sort of unspoken gentleman’s agreement – it would be understood that a particular group or lab was working on one problem and you wouldn’t then go and do that one.

Raymond Gosling

You didn’t go to work on another man’s problem, especially if he’d got a whole team working on it.

Melinda Baldwin

In the Watson and Crick paper, it’s not credited. Watson and Crick say they were stimulated by a general knowledge of the unpublished results of Wilkins and Franklin.

Voice of Nature: John Howe

We have been stimulated by a knowledge of the general nature of the unpublished experimental results and ideas of Dr Wilkins, Dr Franklin and…

Melinda Baldwin

But they don’t cite photo 51 specifically and then Franklin and Gosling, in their paper, say this photo clearly supports the model that Watson and Crick had put forth.

Raymond Gosling

Rosalind’s reaction was, I think, typical of Rosalind. She wasn’t furious or didn’t use the word ‘scooped’. What she actually said was we all stand on each other’s shoulders. We had this second-, third-prize feeling that we were within a millimetre or two of the right answer ourselves.

Melinda Baldwin

So, Watson and Crick had their paper ready to go. They had the structure solved. They wanted to publish it in Nature. Apparently, John Randall, the uber-head of the Kings College London Laboratory, was a member of The Athenaeum, the British social club in London, and so was L. J. F. Brimble, then one of the co-editors of Nature. So, apparently, Brimble approached Randall to say well, we’ve got this paper under consideration, don’t you want the King’s work represented as well? And I think Watson and Crick and Wilkins had already agreed that they would publish two papers side-by-side. Wilkins sort of knew that his work was going to be outshone by Watson and Crick, but he certainly wanted it published. And then apparently after the two of them had agreed to publish the two papers together, Rosalind Franklin said, well, I want a paper on the crystallographic work that Ray Gosling and I did in there as well, and so it was really by conversation by the editors and the heads of the laboratories that the editors agreed to print these paper as quickly as possible. So, famously, the three DNA papers were not peer-reviewed. I think that was quite typically for the Brimble-and-Gale editorship, that they placed a lot of trust in particular laboratory heads and particular friends in the British scientific community and so if Laurence Bragg said that something was good and important, they were going to print it.

Georgina Ferry

There wasn’t a huge fuss made, even within science, about the DNA structure until probably the early 60s when the code began to be cracked because obviously – as Watson and Crick famously said –

Voice of Nature: John Howe

It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.

Georgina Ferry

But the actual code wasn’t cracked until the early 60s, and that was when the power of this discovery really started to make a big difference.

Music: I’ve Got the World on a String by Ella Fitzgerald

Voice of Nature: John Howe

Elsewhere in Nature, Page 757, Appointments vacant. Physicists wanted for fundamental research on felt and applied research of the felt-making industry, The British Hat and Allied Felt-makers Research Association, Manchester.

Music: I’ve Got the World on a String by Ella Fitzgerald

Voice of Nature: John Howe

Page 716, Department of Scientific and Industrial Research UK, The gross expenditure of the department was £5.5 million as against £5 million in the previous year.

Georgina Ferry

The climbing of Mount Everest and the coronation of the Queen and all these things came together so that ’53 in that lab was seen as an almost miraculous time.

Raymond Gosling

Everywhere you looked you could see that it fitted a double helix. It was uncanny. It just screamed at you. I’ve often asked how long would it have been before we as a group saw that and I really don’t know the answer to that. It was a stroke of genius on his part.

Music: I’ve Got the World on a String by Ella Fitzgerald

Voice of Nature: John Howe

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Kerri Smith

The Nature PastCast was produced by me, Kerri Smith, with contributions from Raymond Gosling, writer Georgina Ferry and historian Melinda Baldwin. In episode two of this twelve-part series on the history of science, we’re heading back to the 1980s.