Here is the new ‘joke’ –

What did Watson & Crick discover?

Rosalind Franklin’s notes.

Rosalind Franklin’s Legacy

When it comes to her place in the discovery of the double helix structure of DNA, Rosalind Franklin has not received fair treatment. Or so maintains Lynne Osman Elkin, a professor of biological sciences at California State University, Hayward, who spends much of her time these days trying to clarify Franklin’s significant role in one of the 20th century’s greatest scientific achievements. In March 2003, Elkin published a lengthy article on Franklin in Physics Today, and she’s hard at work on a biography. In this interview, hear what Elkin has to say about exactly where Franklin stands in her mind—and where Photo 51’s creator ought to stand in the history books. Click on highlighted words or phrases for a glossary.

With all she did to make Watson and Crick’s discovery possible, Rosalind Franklin was essentially “a de facto collaborator,” says Lynne Osman Elkin. EnlargePhoto credit: © Novartis Foundation

 

Within reach

NOVA: How close did Franklin actually come to deciphering the structure of DNA?

Elkin: She was very close. She had all the parameters of the helical backbone. She was the one who figured out that there were two forms of DNA, which made solving the whole structure possible. She had figured out that backbone of the A form is antiparallel. It wouldn’t have been very long before she figured out that the B form backbone was antiparallel as well.

The other thing was base-pairing, which was Watson‘s brilliant idea, made possible by chemical information supplied by Jerry Donohue. But if you look at her notebooks, she was very, very aware of hydrogen bonding. She was very, very aware of the difference between enol and keto forms, which were the key to base-pairing. She was aware of Chargaff’s ratios. She was aware of Donohue’s work. All the stuff that circled around base-pairing.

How soon might she have worked it out if Watson and Crick hadn’t gotten her data?

Well, at one time Crick estimated that it would have taken her three months. I don’t know how long it would have taken her, but I think the critical thing with the timing is that she was about to publish her paper on the B form. That’s the March 17th draft that Aaron Klug discovered. And that paper was written well before March 17th, and then after the Watson-Crick structure was figured out, she modified it very minimally, and it became the third Nature paper.

“After Watson saw Photo 51, he went out to dinner with Maurice Wilkins and pressed him for the interpretation of it.”There is no way without her data that Watson and Crick could have figured out the structure before [her March 17th draft] got published. Now, if that had gotten published first and then they figured it out—remember, she talked about the double helix in that paper—then even though they had figured out the actual structure, they would have had to incorporate her information and credit her properly, and she would not have been written out of history.

Franklin’s famous Photo 51, which led to Watson and Crick’s breakthrough insight into the double-helical structure of DNA Enlarge Photo credit: © Franklin, R. and Gosling, R.G./Nature

 

Picture perfect

What did Watson actually get out of Photo 51 beyond the idea that the “X” signified a helix?

After Watson saw Photo 51, he went out to dinner with Wilkins and pressed him for the interpretation of it—the 34-angstrom measurements and so on. At that early date Watson didn’t know how to interpret a diffraction photo, other than that an “X” meant helix. In terms of getting measurements out of it, he hadn’t the foggiest—at that point. It was Wilkins who told him how to interpret it. [For a closer look at the image, see Anatomy of Photo 51.]

What about the idea that the sugar-phosphate groups were on the outside? Did Watson get that from Photo 51?

No. That was from the MRC report. Watson and Crick got a tremendous amount of information from that MRC report. Now, they persisted in wanting to put the bases on the outside. And it’s absurd—you don’t put a hydrophobic thing on the outside of a structure in a cell. You put the hydrophobic stuff on the inside where it’s protected, and the hydrophilic phosphates and sugars on the outside.

As a chemist Franklin knew that automatically, and so did even a graduate student at King’s, Bruce Fraser, when he tried building a model. But Watson and Crick, being weak in their knowledge of chemistry, kept putting it on the outside. And Wilkins said, “You know, Rosalind said it should be on the inside.” So Wilkins once again was telling them information that he knew from Rosalind. They kept resisting, however, because to put it on the inside, it seemed very difficult to know how to pack things.

But when Crick saw the MRC report—in which Franklin had not only said that the phosphates are on the outside but had offered measurements of the interphosphate distances—even he couldn’t argue with that anymore. So when Watson once again was trying to build a model and it wasn’t working, Crick said, “Why don’t you put the phosphates on the outside, like Rosalind said?”