The Double Helix

The Double Helix

by

James D. Watson

Teachers and parents! Our Teacher Edition on The Double Helix makes teaching easy.
X-ray diffraction is an important technique in crystallography. It involves shooting an X-ray beam at a crystal, then measuring how this X-ray beam diffracts (or splits apart in different directions). These diffraction measurements allow crystallographers to determine where different atoms are located inside the crystal. Rosalind Franklin’s X-ray diffraction experiment on DNA gave Crick and Watson the key measurements they needed to model the double helix structure.

X-ray Diffraction Quotes in The Double Helix

The The Double Helix quotes below are all either spoken by X-ray Diffraction or refer to X-ray Diffraction. For each quote, you can also see the other terms and themes related to it (each theme is indicated by its own dot and icon, like this one:
Research, Adventure, and the Thrill of Discovery Theme Icon
).
Chapter 5 Quotes

I proceeded to forget Maurice, but not his DNA photograph. A potential key to the secret of life was impossible to push out of my mind. The fact that I was unable to interpret it did not bother me. It was certainly better to imagine myself becoming famous than maturing into a stifled academic who had never risked a thought.

Related Characters: James D. Watson (speaker), Maurice Wilkins , Herman Kalckar
Page Number: 35
Explanation and Analysis:
Chapter 6 Quotes

Max Perutz was in his office when I showed up just after lunch. […] I explained that I was ignorant of how X-rays diffract, but Max immediately put me at ease. I was assured that no high-powered mathematics would be required: both he and John had studied chemistry as undergraduates. All I need do was read a crystallographic text; this would enable me to understand enough theory to begin to take X-ray photographs.

[…]

When Max realized that I had come directly to the lab from the station and had not yet seen any of the colleges, he altered our course to take me through King’s, along the backs, and through to the Great Court of Trinity. I had never seen such beautiful buildings in all my life, and any hesitation I might have had about leaving my safe life as a biologist vanished.

Related Characters: James D. Watson (speaker), Francis Crick , John Kendrew , Max Perutz
Page Number: 41-42
Explanation and Analysis:
Chapter 7 Quotes

From my first day in the lab I knew I would not leave Cambridge for a long time. Departing would be idiocy, for I had immediately discovered the fun of talking to Francis Crick. Finding someone in Max’s lab who knew that DNA was more important than proteins was real luck. Moreover, it was a great relief for me not to spend full time learning X-ray analysis of proteins. Our lunch conversations quickly centered on how genes were put together. Within a few days after my arrival, we knew what to do: imitate Linus Pauling and beat him at his own game.

Related Characters: James D. Watson (speaker), Francis Crick , Linus Pauling , Max Perutz
Page Number: 48
Explanation and Analysis:

In place of pencil and paper, the main working tools were a set of molecular models superficially resembling the toys of preschool children.
We could thus see no reason why we should not solve DNA in the same way. All we had to do was to construct a set of molecular models and begin to play—with luck, the structure would be a helix.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins , Linus Pauling
Related Symbols: Molecular Models
Page Number: 50-51
Explanation and Analysis:
Chapter 11 Quotes

The wrong person had been sent to hear Rosy. If Francis had gone along, no such ambiguity would have existed. It was the penalty for being oversensitive to the situation. For, admittedly, the sight of Francis mulling over the consequences of Rosy’s information when it was hardly out of her mouth would have upset Maurice. In one sense it would be grossly unfair for them to learn the facts at the same time. Certainly Maurice should have the first chance to come to grips with the problem. On the other hand, there seemed no indication that he thought the answer would come from playing with molecular models. Our conversation on the previous night had hardly alluded to that approach. Of course, the possibility existed that he was keeping something back. But that was very unlikely—Maurice just wasn’t that type.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins
Related Symbols: Molecular Models
Page Number: 76
Explanation and Analysis:
Chapter 16 Quotes

My first X-ray pictures revealed, not unexpectedly, much less detail than was found in the published pictures. Over a month was required before I could get even halfway presentable pictures. They were still a long way, though, from being good enough to spot a helix.

Related Characters: James D. Watson (speaker), Francis Crick
Page Number: 115
Explanation and Analysis:
Chapter 23 Quotes

Interrupting her harangue, I asserted that the simplest form for any regular polymeric molecule was a helix. Knowing that she might counter with the fact that the sequence of bases was unlikely to be regular, I went on with the argument that, since DNA molecules form crystals, the nucleotide order must not affect the general structure. Rosy by then was hardly able to control her temper, and her voice rose as she told me that the stupidity of my remarks would be obvious if I would stop blubbering and look at her X-ray evidence.

[…]

Without further hesitation I implied that she was incompetent in interpreting X-ray pictures. If only she would learn some theory, she would understand how her supposed antihelical features arose from the minor distortions needed to pack regular helices into a crystalline lattice.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins , Linus Pauling
Page Number: 165-166
Explanation and Analysis:

The instant I saw the picture my mouth fell open and my pulse began to race. The pattern was unbelievably simpler than those obtained previously (“A” form). Moreover, the black cross of reflections which dominated the picture could arise only from a helical structure. […] The real problem was the absence of any structural hypothesis which would allow them to pack the bases regularly in the inside of the helix. Of course this presumed that Rosy had hit it right in wanting the bases in the center and the backbone outside. Though Maurice told me he was now quite convinced she was correct, I remained skeptical, for her evidence was still out of the reach of Francis and me.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins , Max Perutz
Page Number: 167-169
Explanation and Analysis:
Chapter 28 Quotes

Rosy’s instant acceptance of our model at first amazed me. I had feared that her sharp, stubborn mind, caught in her self-made antihelical trap, might dig up irrelevant results that would foster uncertainty about the correctness of the double helix. Nonetheless, like almost everyone else, she saw the appeal of the base pairs and accepted the fact that the structure was too pretty not to be true. Moreover, even before she learned of our proposal, the X-ray evidence had been forcing her more than she cared to admit toward a helical structure. The positioning of the backbone on the outside of the molecule was demanded by her evidence and, given the necessity to hydrogen-bond the bases together, the uniqueness of the A-T and G-C pairs was a fact she saw no reason to argue about.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins
Related Symbols: Molecular Models, The Double Helix Structure
Page Number: 210
Explanation and Analysis:
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The Double Helix PDF

X-ray Diffraction Term Timeline in The Double Helix

The timeline below shows where the term X-ray Diffraction appears in The Double Helix. The colored dots and icons indicate which themes are associated with that appearance.
Chapter 1
Research, Adventure, and the Thrill of Discovery Theme Icon
...was working in Max Perutz and Sir Lawrence Bragg’s Cavendish Laboratory, which studied proteins through X-ray diffraction. Crick did some experiments, but he was mainly focused on the theory of protein... (full context)
Chapter 2
Scientific Collaboration, Competition, and Community Theme Icon
Academic Life and the University Theme Icon
...to deal with competition from the American chemist Linus Pauling, who wanted to study his X-ray images of DNA. (full context)
Chapter 3
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
Academic Life and the University Theme Icon
Maurice Wilkins introduced Watson to his X-ray studies of DNA in Naples in 1951, just before Watson met Francis Crick. Watson had... (full context)
Chapter 4
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
Academic Life and the University Theme Icon
...Herman Kalckar’s biochemistry research, which had nothing to do with genetics. He found the conference’s X-ray diffraction crystallographers more interesting, but he tried not to get his hopes up, because their... (full context)
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
Against all odds, Maurice Wilkins’s presentation on X-ray diffraction crystallography astonished Watson. It even included a rudimentary photo of DNA. The next day,... (full context)
Chapter 5
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
After the conference in Naples, Watson couldn’t stop thinking about Maurice Wilkins’s X-ray diffraction photo of DNA, the “key to the secret of life.” He also learned about... (full context)
Scientific Collaboration, Competition, and Community Theme Icon
Academic Life and the University Theme Icon
Watson concluded that he wanted to start learning about X-ray diffraction crystallography. There were three places he could go: Linus Pauling’s lab at Caltech, Maurice... (full context)
Chapter 7
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...explained Linus Pauling’s alpha helix research to Watson. Pauling’s discovery wasn’t based on equations or X-ray diffraction, but rather on a straightforward analysis of how different atoms fit together, using molecular... (full context)
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...knew that they could eliminate plenty of possible structures for DNA if they had good X-ray pictures of it. But the only person with these pictures was Maurice Wilkins. Fortunately, Wilkins... (full context)
Chapter 9
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...crystallographer V. Vand wrote Max Perutz to explain his new theory of how to use X-ray diffraction to study helices. Crick and his colleague Bill Cochran immediately noticed errors in Vand’s... (full context)
Chapter 11
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
Based on Maurice Wilkins and Rosalind Franklin’s X-ray diffraction data, Crick and Watson quickly concluded that “the sugar-phosphate backbone was in the center... (full context)
Chapter 16
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
Academic Life and the University Theme Icon
Watson eagerly showed Bernal and Fankuchen’s X-ray diffraction photo of TMV to Crick, who agreed that it appeared to have a helical... (full context)
Chapter 23
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...noted that there still wasn’t any evidence for DNA having a helical structure at all—her X-ray diffraction evidence disproved the idea. But Watson told her that she interpreted her X-ray data... (full context)
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...also nearly attacked him once. He revealed that he and his assistant were copying Franklin’s X-ray diffraction images, and that Franklin discovered a new form of DNA (the “B” form). Wilkins... (full context)
Chapter 28
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...double helix structure. Next, Wilkins returned to London to check the model against his lab’s X-ray diffraction data. To Watson’s relief, Wilkins was excited, not bitter or resentful. Two days later,... (full context)
Chapter 29
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...and Watson’s discovery. Not only did they beat Linus Pauling, but they also used the X-ray technique that Bragg invented decades earlier. Watson’s sister Elizabeth agreed to type up the final... (full context)