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Chapter 24
Themes
Key
LitCharts assigns a color and icon to each theme in The Double Helix, which you can use to track the themes throughout the work.
Research, Adventure, and the Thrill of Discovery
Scientific Collaboration, Competition, and Community
DNA and the Secret of Life
Academic Life and the University
Summary
Analysis
Over the following days, Crick started to grow uneasy with how little time Watson spent in the lab. Almost every day, he played tennis in the afternoon, had drinks with French girls at the boarding house after tea, and went to the movies at night. But he also thought 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 had these data—actually, they got them because Max Perutz was part of the oversight committee assessing Maurice Wilkins and Rosalind Franklin’s lab.
Crick and Watson approached their research in different but complementary ways: Crick spent his days poring over data and models in the lab, while Watson tried to stimulate his creativity by enjoying himself. Meanwhile, Watson again points out that he technically wasn’t authorized to use Rosalind Franklin’s data—but he avoids addressing the serious ethical questions that this raises.
Themes
When Watson got home every night, he sketched out different structures for the four nitrogenous bases. He needed to figure out how to position the bases on the 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 did hold the two strands together. But he needed to figure out how this was possible.
Crick and Watson knew that DNA could be structurally separated into two main parts: the sugar-phosphate backbone that holds the molecule together and the nitrogenous bases that encode genetic information by forming a specific sequence. This is why Watson needed to figure out how the molecule could accommodate an irregular order in the bases while maintaining a regular shape in the molecule overall. But since the bases were all different shapes and sizes, in theory, an irregular order of bases should have created an irregularly shaped molecule.
Themes
A week later, Watson thought up a possible solution. He remembered that adenine, thymine, guanine, and cytosine can all hydrogen bond with themselves. Therefore, perhaps the two strands of DNA could have the same sequence of nitrogenous bases, with hydrogen bonds holding them together. But 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, if DNA has two identical chains, then one was likely the template for the other. This means that the DNA structure would likely hold the secret to gene replication, too. That night, lying in bed, Watson was overcome with wonder at this idea.
Watson’s feeling of utter wonder and exhilaration shows why science can be so emotionally and psychologically rewarding: it’s like solving a profoundly important puzzle. While Watson knew that his newest theory wasn’t perfect, he also recognized that it was a major step forward. If the vertical sugar-phosphate backbones are on the outside of the DNA molecule, and the nitrogenous bases point inwards horizontally, then hydrogen bonds between the bases can hold the two strands of DNA together, like the rungs in a ladder. But if these nitrogenous bases are always identical on both sides, then every rung on the ladder will have a different shape (because so do all four of the bases). Therefore, the DNA molecule would be full of bulges and indentations.
Themes
