84 pages • 2 hours read
James D. WatsonThe Double Helix
Nonfiction | Book | Adult | Published in 1968A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 5-8Chapter Summaries & Analyses
Chapter 5 Summary
Stopping off in Geneva, Watson is excited to hear rumours that Pauling, at Cal Tech, has partly solved the structures of proteins. He gets the information from a scientist in Geneva who attended the lecture where Pauling announced his discovery.
The lecture, we’re told, was full of “dramatic flair” (25), with Pauling revealing the model of his revolutionary a-helix with showbiz panache. Watson immediately starts thinking about whether Pauling’s model and approach can be applied to DNA.
Back in Copenhagen he reads Pauling’s published article, admires his style, and fancifully imagines emulating it. What he’s seen from Wilkins and Pauling lead Watson to seek out somewhere where he can study x-ray diffraction. Knowing vaguely about the work being done at the Cavendish, he makes enquiries through Luria. As luck has it Luria knows John Kendrew, who works in the lab, and is able to get Watson a provisional place.
His fellowship in Copenhagen almost over, Watson puts off writing the letter to his home university to explain his new direction until his place at Cambridge is secure.
Meanwhile, he continues experiments and attends an International Phage Conference, which is thoroughly enjoyable owing to the night-life and free champagne. He starts to realise “a scientist’s life might be interesting socially as well as intellectually” (28).
Chapter 6 Summary
Watson arrives at the Cavendish and is greeted by Perutz. He admits he knows little of x-ray diffraction but is put at ease about it.
Pertuz shows Watson around Cambridge, to help him find accommodations, and Watson is struck by the beauty of the city, which offsets his cold and poky student quarters.
The next day, he meets Bragg, who formally confirms his admittance to the Cavendish. Watson’s initial impression of Bragg is of a fusty old English gent, probably in “effective retirement” (30), but he reflects how wrong he was to be about this, and notes the active interest Bragg was to take in genes.
Watson returns to Copenhagen to tie things up and give formal notice to his home university in Washington of his plans. He heads directly back to Cambridge, assuming his plans will be approved, but finds that a new director in Washington has refused approval, “since he was unqualified to do crystallographic work” (31). (Implicitly it’s understood that Watson has overstepped his bounds). Despite attempts to reach a diplomatic solution, the board postpones the decision and Watson faces a spell in Cambridge without funding.
The generosity of the grant from his time at Copenhagen still leaves him enough to live off of. He moves into a small room at Kendrew’s house, which despite being damp is convenient and cheap to rent.
Chapter 7 Summary
This chapter describes Watson’s early work on DNA with Crick and outlines their approach.
Watson immediately feels at home upon meeting Crick, who shares his passion for DNA, and the two start working on the problem together. They are both officially working on proteins, but they take several hours a week over their lunch to talk DNA.
Watson is relieved his experimental work with Kendrew on horse myoglobin doesn’t show much promise, so he’s free to focus more time on DNA.
Watson and Crick share the belief that Pauling’s approach to solving protein structure by “relying on the simple laws of structural chemistry” (34) and building viable molecular models could be applied to DNA.
Watson runs over their ideas at this stage: DNA must contain a large number of nucleotide linears linked together in a regular way. If the links weren’t regular, they wouldn’t be able to form the crystalline structures that Wilkins had observed.
The possibility of a helix structure was appealing as a regular, linkable pattern. Their first line of attack is to assume a regular sugar phosphate backbone for the DNA molecule and look for “a helical three-dimensional configuration in which all the backbone groups had identical chemical environments” (36).
Pauling’s a-helix comprised a single polypeptide chain, but the X-ray evidence for DNA already suggests a thicker compound, so they assume a compound helix - two or more nucleotide chains twisted around each other and held together by hydrogen bonds or salt linkage.
A further complication is the arrangement of the 4 nucleotides found in DNA:
Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).
These four nucleotides are regular in that each contains a sugar and phosphate component, but unique in that their nitrogenous bases are different: either purine or pyrimidine. From this they postulate a regular sugar phosphate backbone and irregular bases, which would allow for the variation inherent in DNA as genetic code.
Real progress depends on Wilkins’ x-ray images. Crick invites him to Cambridge. Wilkins similarly believes a compound helical structure is likely, but is not convinced by their model-building approach. He talks about Franklin, and explains the situation has worsened, to the point that she won’t share her latest results with him. Instead, they have to wait for a talk she would be giving in three weeks’ time.
Chapter 8 Summary
One month after Watson’s arrival, drama occurs between Crick and Bragg. After reading a new paper co-authored by Bragg and Perutz on haemoglobin molecules, Cricks is enraged that an idea he’d put forward months earlier has been used without acknowledgement.
He confronts Bragg in his office. Bragg denies any knowledge of Crick’s idea and an argument ensues, fuelled by long-standing tension. After, Crick fears for his long-term position at the Cavendish. Bragg clearly wants rid of him, and despite Crick’s abilities, he has no substantial achievement to defend his worth.
There follows some academic background on Crick. He originally studied physics, served in the Admiralty’s Science Department during the war, and after moved to Cambridge to do biology. In 1949, he began a PhD under Perutz’s supervision.
Perutz and Kendrew help resolve the argument between Crick and Bragg. They confirm Crick has written something of the matter previously, even though it was unknown to Bragg, and both agree they came to the idea independently. Normal business resumes.
Chapters 5-8 Analysis
These chapters cover the arrival of Watson in Cambridge, where the work on DNA proper begins in partnership with Crick. They trace Watson’s intellectual and literal journey to this point and his first impression of his new home. Chapter 7 is particularly important in establishing the scientific ideas and approach Crick and Watson adopted toward DNA, and the influence of Lining’s work. We also see a development of several key themes.
Watson is prepared to take a significant gamble (both scientific and personal) in prematurely breaking his fellowship in Copenhagen and moving to Cambridge to begin work on crystallography, a field he knows little about. As discussed in the last section he has a clear focus on DNA, and a talent for cutting through impediments to get closer to the heart of the matter.
Many wouldn’t make this kind of leap into the unknown, preferring to stick with familiar terrain and not ruffle official feathers. This brings us back to the “human” dimension of the way science develops that Watson mentions in the Preface. It’s not just about scientific knowledge or talent, but, here, a certain boldness and willingness to take risks. The risk of giving offence, of entering a field one doesn’t understand, of simply trying something new. Watson shows again and again he is prepared to take these risks and take advantage of circumstance because he senses the possibility of a great discovery and wants to be a part of it.
In Chapter 5, he makes this point explicitly; he isn’t fazed that he can’t interpret Wilkins’ x-ray image. Better to gamble, than “maturing into a stifled academic who had never risked a thought” (25).
Informing his motivation is a perceived dichotomy between two versions of the scientist, two possible destinies that lie ahead. One is the plodding, everyday scientist, with which Watson links his “second-rate” experiments in Copenhagen. The other is the scientist of the bold and glamorous world of cutting edge discoveries, for which he finds a living model in Pauling.
As much as a quest for truth, it is personal ambition that drives Watson towards the riddle of DNA, and this ideal of the great scientist. We see signs of this when he mentions daydreaming of emulating Pauling’s style when writing up his own imagined discoveries.
In contrast to the image of the “stifled academic,” we have Pauling, who conducts himself with “dramatic flair” (25) and panache. Here, Watson’s frankness again comes into play. He doesn’t profess purely noble aspirations, but lays bare how far the drive to prove himself, and the allure of personal glory, were motivating factors.
In Crick, he finds someone with a similar passion not just for DNA, but for achieving greatness, a fellow maverick and speculator but one whose approach is different in its own way. His thinking is both more expansive and diffuse than Watson’s. It is their combination (both human and scientific) that will ultimately lead to success.
Another “human” element to consider is the support Watson receives from various quarters: people who are willing to take a gamble on him. Luria, Kendrew, Perutz, Kalckar, even a random Cambridge biochemist are all prepared to go out of their way to help.
Bragg presents an interesting alternative model of the scientist: the old accomplished figure whose glories are seemingly behind him. At first meeting, Watson sees him as a “curiosity out of the past” (30), suffused with English formality, but he quickly revises this opinion, noting Bragg’s active involvement in the latest developments at the Cavendish.
Bragg forms an obvious counterpoint to Crick’s energetic and imposing presence, but also, more subtly, to the dazzling performances of Pauling. Bragg too has accomplished great things, but his style is reserved and retiring.
The altercation between Bragg and Cricks serves as a convenient dramatic aside from the more focused science of Chapter 7. It shows that Watson is keen to keep a balance, as a writer. But it also underlines again that moral dilemma about intellectual ownership in science, and shows how ambiguous and sensitive an issue it can be.
Linked to Watson’s first impression of Bragg is the wider issue of his first real impression of England, as a young American. He sees in Bragg a formality, an antiquated quality, which is conceived of as typically English; perhaps outmoded, but not without its charm. He is stunned by the beauty of the Cambridge colleges, but their grandeur is immediately contrasted to the reality of the damp, cold quarters he has to inhabit.
Chapter 7 is also key in understanding Watson and Crick’s scientific approach. Watson and Crick’s approach to DNA draws heavily on Pauling’s structural chemistry and molecular modelling, and the hope that DNA might have a regular helical structure, similar to the one Pauling found in certain protein chains.
The helix is the central symbol and subject of this book. It is a regular spiralling shape, and its appeal as a possible model for DNA is the way it can accommodate the regularity needed for long chains to be formed, while also accommodating the variety inherent in genetic material. It is a building block of sorts, and its regularity means that it could potentially be solved. We have to remember that at the time it was simply an idea, a conjecture, a hunch. The appeal of its simplicity was linked to a sense of its elegance and beauty.
What Watson learns from Pauling and stresses in this chapter is the appeal of simplicity: look to find the simple solution first, assume nature is efficient and simple in its organisation: “Pauling never got anywhere by seeking out messes” (36).
Structural chemistry can be described as a kind of molecular theorising. One considers “which atoms like to sit next to each other” (35) based on the laws of chemistry, and build up possible 3D models of molecules from there. Like Pauling, Watson and Crick began using models “superficially resembling the toys of pre-school children” to explore possible solutions (36).
They know at this stage something of the chemical components of DNA; what they don’t know is how it all fits together. The situation could be likened to trying to construct a complex three-dimensional jigsaw with an uncertain number of pieces, and no definite sense of what the finished puzzle is supposed to look like. The laws of chemistry here are equivalent to the cuts and indents in the pieces which determine how, and if, they fit. The pieces themselves are the nucleotides (organic molecules from which DNA is formed).
The picture on the front of the puzzle box is what Wilkins and Franklin are working on reconstructing in their London lab through x-ray diffraction.
In the absence of access to Wilkins’ and Franklin’s experimental data, it’s easy to see how Watson and Crick saw structural chemistry and trial-and-error modelling as a good point of attack.
