The Information - James Gleick [138]
The whole set of instructions—situated “somewhere in the chromosomes”—is the genome. This is a “catalogue,” he said, containing, if not all, then at least “a substantial fraction of all information about an adult organism.” He emphasized, though, how little was known about genes. Were they discrete physical entities, or did they overlap? Were they “independent sources of information” or did they affect one another? How many were there? Multiplying all these unknowns, he arrived at a result:
that the essential complexity of a single cell and of a whole man are both not more than 1012 nor less than 105 bits; this is an extremely coarse estimate, but is better than no estimate at all.♦
These crude efforts led to nothing, directly. Shannon’s information theory could not be grafted onto biology whole. It hardly mattered. A seismic shift was already under way: from thinking about energy to thinking about information.
Across the Atlantic, an odd little letter arrived at the offices of the journal Nature in London in the spring of 1953, with a list of signatories from Paris, Zurich, Cambridge, and Geneva, most notably Boris Ephrussi, France’s first professor of genetics.♦ The scientists complained of “what seems to us a rather chaotic growth in technical vocabulary.” In particular, they had seen genetic recombination in bacteria described as “transformation,” “induction,” “transduction,” and even “infection.” They proposed to simplify matters:
As a solution to this confusing situation, we would like to suggest the use of the term “interbacterial information” to replace those above. It does not imply necessarily the transfer of material substances, and recognizes the possible future importance of cybernetics at the bacterial level.
This was the product of a wine-flushed lakeside lunch at Locarno, Switzerland—meant as a joke, but entirely plausible to the editors of Nature, who published it forthwith.♦ The youngest of the lunchers and signers was a twenty-five-year-old American named James Watson.
The very next issue of Nature carried another letter from Watson, along with his collaborator, Francis Crick. It made them famous. They had found the gene.
A consensus had emerged that whatever genes were, however they functioned, they would probably be proteins: giant organic molecules made of long chains of amino acids. Alternatively, a few geneticists in the 1940s focused instead on simple viruses—phages. Then again, experiments on heredity in bacteria had persuaded a few researchers, Watson and Crick among them, that genes might lie in a different substance, which, for no known reason, was found within the nucleus of every cell, plant and animal, phages included.♦ This substance was a nucleic acid, particularly deoxyribonucleic acid, or DNA. The people working with nucleic acids, mainly chemists, had not been able to learn much about it, except that the molecules were built up from smaller units, called nucleotides. Watson and Crick thought this must be the secret, and they raced to figure out its structure at the Cavendish Laboratory in Cambridge. They could not see these molecules; they could only seek clues in the shadows cast by X-ray diffraction. But they knew a great deal about the subunits. Each nucleotide contained a “base,” and there were just four different bases, designated as A, C, G, and T. They came in strictly predictable