A short history of nearly everything - Bill Bryson [205]
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