Bill Bryson - A short history of nearly everything

However, she did have the best images in existence of the possible structure of DNA, achieved by means of X-ray crystallography, the technique perfected by Linus Pauling. Crystallography had been used successfully to map atoms in crystals (hence “crystallography”), but DNA molecules were a much more finicky proposition. Only Franklin was managing to get good results from the process, but to Wilkins’s perennial exasperation she refused to share her findings.

If Franklin was not warmly forthcoming with her findings, she cannot be altogether blamed. Female academics at King’s in the 1950s were treated with a formalized disdain that dazzles modern sensibilities (actually any sensibilities). However senior or accomplished, they were not allowed into the college’s senior common room but instead had to take their meals in a more utilitarian chamber that even Watson conceded was “dingily pokey.” On top of this she was being constantly pressed-at times actively harassed-to share her results with a trio of men whose desperation to get a peek at them was seldom matched by more engaging qualities, like respect. “I’m afraid we always used to adopt-let’s say a patronizing attitude toward her,” Crick later recalled. Two of these men were from a competing institution and the third was more or less openly siding with them. It should hardly come as a surprise that she kept her results locked away.

That Wilkins and Franklin did not get along was a fact that Watson and Crick seem to have exploited to their benefit. Although Crick and Watson were trespassing rather unashamedly on Wilkins’s territory, it was with them that he increasingly sided-not altogether surprisingly since Franklin herself was beginning to act in a decidedly queer way. Although her results showed that DNA definitely was helical in shape, she insisted to all that it was not. To Wilkins’s presumed dismay and embarrassment, in the summer of 1952 she posted a mock notice around the King’s physics department that said: “It is with great regret that we have to announce the death, on Friday 18th July 1952 of D.N.A. helix. . . . It is hoped that Dr. M.H.F. Wilkins will speak in memory of the late helix.”

The outcome of all this was that in January 1953, Wilkins showed Watson Franklin’s images, “apparently without her knowledge or consent.” It would be an understatement to call it a significant help. Years later Watson conceded that it “was the key event . . . it mobilized us.” Armed with the knowledge of the DNA molecule’s basic shape and some important elements of its dimensions, Watson and Crick redoubled their efforts. Everything now seemed to go their way. At one point Pauling was en route to a conference in England at which he would in all likelihood have met with Wilkins and learned enough to correct the misconceptions that had put him on the wrong line of inquiry, but this was the McCarthy era and Pauling found himself detained at Idlewild Airport in New York, his passport confiscated, on the grounds that he was too liberal of temperament to be allowed to travel abroad. Crick and Watson also had the no less convenient good fortune that Pauling’s son was working at the Cavendish and innocently kept them abreast of any news of developments and setbacks at home.

Still facing the possibility of being trumped at any moment, Watson and Crick applied themselves feverishly to the problem. It was known that DNA had four chemical components-called adenine, guanine, cytosine, and thiamine-and that these paired up in particular ways. By playing with pieces of cardboard cut into the shapes of molecules, Watson and Crick were able to work out how the pieces fit together. From this they made a Meccano-like model-perhaps the most famous in modern science-consisting of metal plates bolted together in a spiral, and invited Wilkins, Franklin, and the rest of the world to have a look. Any informed person could see at once that they had solved the problem. It was without question a brilliant piece of detective work, with or without the boost of Franklin’s picture.

The April 25, 1953, edition of Nature carried a 900-word article by Watson and Crick titled “A Structure for Deoxyribose Nucleic Acid.” Accompanying it were separate articles by Wilkins and Franklin. It was an eventful time in the world-Edmund Hillary was just about to clamber to the top of Everest while Elizabeth II was imminently to be crowned queen of England-so the discovery of the secret of life was mostly overlooked. It received a small mention in the News Chronicle and was ignored elsewhere.

Rosalind Franklin did not share in the Nobel Prize. She died of ovarian cancer at the age of just thirty-seven in 1958, four years before the award was granted. Nobel Prizes are not awarded posthumously. The cancer almost certainly arose as a result of chronic overexposure to X-rays through her work and needn’t have happened. In her much-praised 2002 biography of Franklin, Brenda Maddox noted that Franklin rarely wore a lead apron and often stepped carelessly in front of a beam. Oswald Avery never won a Nobel Prize either and was also largely overlooked by posterity, though he did at least have the satisfaction of living just long enough to see his findings vindicated. He died in 1955.

Watson and Crick’s discovery wasn’t actually confirmed until the 1980s. As Crick said in one of his books: “It took over twenty-five years for our model of DNA to go from being only rather plausible, to being very plausible . . . and from there to being virtually certainly correct.”

Even so, with the structure of DNA understood progress in genetics was swift, and by 1968 the journal Science could run an article titled “That Was the Molecular Biology That Was,” suggesting-it hardly seems possible, but it is so-that the work of genetics was nearly at an end.

In fact, of course, it was only just beginning. Even now there is a great deal about DNA that we scarcely understand, not least why so much of it doesn’t actually seem to do anything. Ninety-seven percent of your DNA consists of nothing but long stretches of meaningless garble-“junk,” or “non-coding DNA,” as biochemists prefer to put it. Only here and there along each strand do you find sections that control and organize vital functions. These are the curious and long-elusive genes.

Genes are nothing more (nor less) than instructions to make proteins. This they do with a certain dull fidelity. In this sense, they are rather like the keys of a piano, each playing a single note and nothing else, which is obviously a trifle monotonous. But combine the genes, as you would combine piano keys, and you can create chords and melodies of infinite variety. Put all these genes together, and you have (to continue the metaphor) the great symphony of existence known as the human genome.

An alternative and more common way to regard the genome is as a kind of instruction manual for the body. Viewed this way, the chromosomes can be imagined as the book’s chapters and the genes as individual instructions for making proteins. The words in which the instructions are written are called codons, and the letters are known as bases. The bases-the letters of the genetic alphabet-consist of the four nucleotides mentioned a page or two back: adenine, thiamine, guanine, and cytosine. Despite the importance of what they do, these substances are not made of anything exotic. Guanine, for instance, is the same stuff that abounds in, and gives its name to, guano.

The shape of a DNA molecule, as everyone knows, is rather like a spiral staircase or twisted rope ladder: the famous double helix. The uprights of this structure are made of a type of sugar called deoxyribose, and the whole of the helix is a nucleic acid-hence the name “deoxyribonucleic acid.” The rungs (or steps) are formed by two bases joining across the space between, and they can combine in only two ways: guanine is always paired with cytosine and thiamine always with adenine. The order in which these letters appear as you move up or down the ladder constitutes the DNA code; logging it has been the job of the Human Genome Project.