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The molecular structure of DNA — and a dream staircase that wasn’t

Check, recheck and check again to determine whether fantastic science stories are real or just fairy tales.

This article was first published in the Montreal Gazette.

James Watson had a dream in which he was walking up a spiral staircase. He and Francis Crick had been working on the structure of DNA at the Cavendish Laboratories in England, but were stymied by the problem, until Watson had his dream. The vision of the spiral staircase was the key to determining the double helical structure of DNA. The story is so alluring that I have told it many times.

In the early 1950s, Watson and Crick were in a race with California Institute of Technology chemistry professor Linus Pauling to unravel the structure of DNA, a molecule that had been isolated from the nucleus of cells way back in 1869 by Swiss biologist Friedrich Miescher. It took another 70 years before DNA was identified as the molecule that contains the instructions for organisms to develop, survive and reproduce. How it serves as the “blueprint of life” was a mystery, the solution of which required the determination of DNA’s exact molecular structure.

By the 1940s, it had become clear that DNA is a long molecule made up of units called nucleotides, linked in a chain and that when a cell divides, its DNA is reproduced with the new cells containing identical copies. How does this happen? Pauling did not tackle the problem of reproduction, but he did propose that DNA was not just a single strand of nucleotides but was a complex structure with three strands wound together in a triple helix.

Crick and Watson had been trying to build models of DNA with sticks and balls and did not see how Pauling’s theory would lead to a stable structure. That’s when Watson had the dream he shared with Crick. They quickly built a model in which two strands of DNA were wound together like the railings of a spiral staircase, connected by the steps. If the steps were broken, each strand could form as a model for nucleotides to assemble into a new strand.

In typical British understatement, they concluded their 1953 paper — one of the most cited in history — by stating: “It has not escaped our notice that the specific pairing we have postulated suggests a possible copying mechanism for the genetic material.”

A great story, right? As I approach close to half a century of being in the business of communicating science to students and the public, I’m sometimes asked about what I myself have learned. I would say that “check and recheck” is at the top of the list.

When I first started out, I was quite naive about the extent of incorrect information floating about. It wasn’t until the emergence of the internet and social media that I became acutely aware of the problem and the importance of separating myth from fact. That became a burning passion, with plenty of fuel added to the fire by the misinformation spread around when that nasty virus brought the world to a halt in 2019. Of course, COVID isn’t the only fodder for firing blanks at the public; there are plenty of “alternative facts,” half-truths and outright deceptions out there when it comes to climate change, nutrition, medications, personal care products, environmental chemicals and history. So now when I tackle a topic, I check and recheck my sources.

When I was preparing a lecture on biotechnology — one in which I have always recounted the story of Watson’s dream — it occurred to me that I should check that appealing tale. Off into the world of Google I went. There were numerous accounts of the dream escapade with virtually all claiming Watson himself as the source and many referencing a 2005 TED talk in which he talked about the dream. I proceeded to track down the talk How We Discovered DNA, a title that could not have come from Watson, since of course DNA had been known for over a century. Curiously, even ChatGPT wrongly claims that Crick and Watson discovered DNA, underlining its unreliability.

What Crick and Watson discovered was the molecular structure of DNA, as nicely described by Watson with even a little humour thrown in. But not one word about any sort of dream! Surely it would have been mentioned in a talk that focused on this epic discovery. Then I decided to reread Watson’s book, The Double Helix: A Personal Account of the Discovery of the Structure of DNA.

Surely the dream would be part of a personal account.

Not a mention. Just to be sure, I did a search for the word “dream” in the book — still no dream of any staircase, or of coiled snakes, another version mentioned by some pseudo-historians. I am forced to conclude that someone dreamed up the dream story.

The fact is that the key to the structure of DNA was not found in a dream, but in an X-ray diffraction photograph of crystalline DNA taken by Rosalind Franklin. She concluded that DNA was helical but could go no further. It remained for Crick and Watson to work out the details, for which they received the Nobel Prize in 1962. Franklin should have shared but she had died from cancer at a young age and the Prize cannot be awarded posthumously.

Having chastised myself for repeatedly telling the dream story without verifying, I wondered if another similar account I was fond of telling was also a fairy tale. I had read numerous narratives about Otto Loewi’s classic 1921 experiment proving the existence of neurotransmitters that resulted in his being awarded the 1936 Nobel Prize in Medicine and Physiology. Loewi stimulated the vagus nerve connected to a freshly isolated frog heart that was still beating and noted that the beat slowed. When he took some of the fluid in which the heart was immersed and dripped it over a second beating heart, it too slowed without having been electrically stimulated. The only explanation was that stimulation of the nerve caused a chemical to be released that slowed the heartbeat. That chemical was the first neurotransmitter to be isolated and was identified as acetylcholine by Henry Dale, who shared the Nobel with Loewi.

Reports of Loewi’s discovery always cite his own account of how the crucial experiment came to him in a dream that made him jump out of bed, rush to the lab and dissect those famous frogs. I had to investigate. It turns out that Loewi had told the story to a number of friends, including Dale, who in his biography of Loewi referred to the dream. Interesting. But then I went to the horse’s mouth, as it were, and dug out Loewi’s autobiography.

“The night before Easter Sunday of that year I awoke, turned on the light, and jotted down a few notes. Then I fell asleep again. It occurred to me at 6 o’clock in the morning that during the night I had written down something most important, but I was unable to decipher the scrawl. The next night, at 3 o’clock, the idea returned. It was the design of an experiment to determine whether or not the hypothesis of chemical transmission that I had uttered 17 years ago was correct. I got up immediately, went to the laboratory, and performed a simple experiment on a frog heart according to the nocturnal design.”

So, not exactly a dream, but the result of thoughts rumbling through the mind during the night, something we are all familiar with. I will have to modify this story as well. I’m glad I checked. And rechecked.


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