The Information - James Gleick [140]
Gamow himself began impulsively by designing a combinatorial code. As he saw it, the problem was to get from the four bases in DNA to the twenty known amino acids in proteins—a code, therefore, with four letters and twenty words.♦ Pure combinatorics made him think of nucleotide triplets: three-letter words. He had a detailed solution—soon known as his “diamond code”—published in Nature within a few months. A few months after that, Crick showed this to be utterly wrong: experimental data on protein sequences ruled out the diamond code. But Gamow was not giving up. The triplet idea was seductive. An unexpected cast of scientists joined the hunt: Max Delbrück, an ex-physicist now at Caltech in biology; his friend Richard Feynman, the quantum theorist; Edward Teller, the famous bomb maker; another Los Alamos alumnus, the mathematician Nicholas Metropolis; and Sydney Brenner, who joined Crick at the Cavendish.
They all had different coding ideas. Mathematically the problem seemed daunting even to Gamow. “As in the breaking of enemy messages during the war,” he wrote in 1954, “the success depends on the available length of the coded text. As every intelligence officer will tell you, the work is very hard, and the success depends mostly on luck.… I am afraid that the problem cannot be solved without the help of electronic computer.”♦ Gamow and Watson decided to make it a club: the RNA Tie Club, with exactly twenty members. Each member received a woolen tie in black and green, made to Gamow’s design by a haberdasher in Los Angeles. The game playing aside, Gamow wanted to create a communication channel to bypass journal publication. News in science had never moved so fast. “Many of the essential concepts were first proposed in informal discussions on both sides of the Atlantic and were then quickly broadcast to the cognoscenti,” said another member, Gunther Stent, “by private international bush telegraph.”♦ There were false starts, wild guesses, and dead ends, and the established biochemistry community did not always go along willingly.
“People didn’t necessarily believe in the code,” Crick said later. “The majority of biochemists simply weren’t thinking along those lines. It was a completely novel idea, and moreover they were inclined to think it was oversimplified.”♦ They thought the way to understand proteins would be to study enzyme systems and the coupling of peptide units. Which was reasonable enough.
They thought protein synthesis couldn’t be a simple matter of coding from one thing to another; that sounded too much like something a physicist had invented. It didn’t sound like biochemistry to them.… So there was a certain resistance to simple ideas like three nucleotides’ coding an amino acid; people thought it was rather like cheating.
Gamow, at the other extreme, was bypassing the biochemical details to put forward an idea of shocking simplicity: that any living organism is determined by “a long number written in a four-digital system.”♦ He called this “the number of the beast” (from Revelation). If two beasts have the same number, they are identical twins.
By now the word code was so deeply embedded in the conversation that people seldom paused to notice how extraordinary it was to find such a thing—abstract symbols representing arbitrarily different abstract symbols—at work in chemistry, at the level of molecules. The genetic code performed a function with uncanny similarities to the metamathematical code invented by Gödel for his philosophical purposes. Gödel’s code substitutes plain numbers for mathematical expressions and operations; the genetic code uses triplets