The Double Helix

The Double Helix

by

James D. Watson

Teachers and parents! Our Teacher Edition on The Double Helix makes teaching easy.
The sugar-phosphate backbone is the chain of alternating phosphate groups and deoxyribose sugars that holds together a series of different nucleotides. DNA has two sugar-phosphate backbones, which wrap around each other in a helical structure and hold the molecule together.

Sugar-Phosphate Backbone Quotes in The Double Helix

The The Double Helix quotes below are all either spoken by Sugar-Phosphate Backbone or refer to Sugar-Phosphate Backbone. 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 23 Quotes

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 24 Quotes

Though I kept insisting that we should keep the backbone in the center, I knew none of my reasons held water. Finally over coffee I admitted that my reluctance to place the bases inside partially arose from the suspicion that it would be possible to build an almost infinite number of models of this type. Then we would have the impossible task of deciding whether one was right. But the real stumbling block was the bases. As long as they were outside, we did not have to consider them. If they were pushed inside, the frightful problem existed of how to pack together two or more chains with irregular sequences of bases. Here Francis had to admit that he saw not the slightest ray of light.

Related Characters: James D. Watson (speaker), Francis Crick , Rosalind Franklin , Maurice Wilkins , Linus Pauling
Related Symbols: Molecular Models
Page Number: 177-178
Explanation and Analysis:
Chapter 25 Quotes

My aim was somehow to arrange the centrally located bases in such a way that the backbones on the outside were completely regular—that is, giving the sugar-phosphate groups of each nucleotide identical three-dimensional configurations. But each time I tried to come up with a solution I ran into the obstacle that the four bases each had a quite different shape. Moreover, there were many reasons to believe that the sequences of the bases of a given polynucleotide chain were very irregular. Thus, unless some very special trick existed, randomly twisting two polynucleotide chains around one another should result in a mess. In some places the bigger bases must touch each other, while in other regions, where the smaller bases would lie opposite each other, there must exist a gap or else their backbone regions must buckle in.

Related Characters: James D. Watson (speaker), Francis Crick
Page Number: 182-183
Explanation and Analysis:

Despite the messy backbone, my pulse began to race. If this was DNA, I should create a bombshell by announcing its discovery. The existence of two intertwined chains with identical base sequences could not be a chance matter. Instead it would strongly suggest that one chain in each molecule had at some earlier stage served as the template for the synthesis of the other chain. Under this scheme, gene replication starts with the separation of its two identical chains.

Related Characters: James D. Watson (speaker), Francis Crick
Page Number: 184-186
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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Sugar-Phosphate Backbone Term Timeline in The Double Helix

The timeline below shows where the term Sugar-Phosphate Backbone appears in The Double Helix. The colored dots and icons indicate which themes are associated with that appearance.
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
...Wilkins and Rosalind Franklin’s X-ray diffraction data, Crick and Watson quickly concluded that “the sugar-phosphate backbone was in the center of the [DNA] molecule.” However, they still had to figure out... (full context)
Chapter 14
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...already realized that their model simply didn’t work because it was impossible for the sugar-phosphate backbone to fit in the middle of the helix. Plus, they couldn’t expect Maurice Wilkins and... (full context)
Chapter 22
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
Peter Pauling explained that his father modeled DNA as “a three-chain helix with the sugar-phosphate backbone in the center”—almost exactly what Watson and Crick thought a year before. But when Watson... (full context)
Chapter 23
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
DNA and the Secret of Life Theme Icon
...agreed, but he explained that the real problem was where the nitrogenous bases and sugar-phosphate backbone were located. Watson explained his fear that Linus Pauling would quickly find the solution, but... (full context)
Chapter 24
Research, Adventure, and the Thrill of Discovery Theme Icon
...two-chain model of DNA. For the first day and a half, he put the sugar-phosphate backbone in the center and the nitrogenous bases on the outside, but he couldn’t come up... (full context)
Chapter 25
Research, Adventure, and the Thrill of Discovery Theme Icon
Scientific Collaboration, Competition, and Community Theme Icon
Academic Life and the University Theme Icon
...constantly about his DNA research. He knew that he had a possible shape for the backbone, and that it was consistent with Rosalind Franklin’s experimental data. However, nobody knew that he... (full context)
DNA and the Secret of Life Theme Icon
...inside of the structure in an irregular order, without disrupting the consistent shape of the backbones. Moreover, a recent paper had convinced him that, contrary to his previous assumptions, hydrogen bonds... (full context)
Research, Adventure, and the Thrill of Discovery Theme Icon
DNA and the Secret of Life Theme Icon
...the problem with this theory is that the different bases have different sizes, so the backbone wouldn’t be able to have a consistent shape. Still, the idea was promising. In fact,... (full context)
Chapter 26
Research, Adventure, and the Thrill of Discovery Theme Icon
DNA and the Secret of Life Theme Icon
...two-strand DNA molecule with an irregular series of nitrogenous bases could still have a regularly-shaped backbone. In this structure, adenine and thymine would always bond together, as would guanine and cytosine.... (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
...his newer one succeed. The organic chemist Alexander Todd also visited and confirmed the sugar-phosphate backbone structure. Then, Watson left Cambridge for a week-long trip to Paris. (full context)