Life's Greatest Secret Read Online Free Page B

sophisticated theory of the nature of the gene that existed at the time, the Three-Man Paper by Timoféef-Ressovsky, Zimmer and Delbrück.
    As Schrödinger explored the nature of heredity for his audience, he was forced to come up with an explanation of what exactly a gene contained. With nothing more than logic to support his hypothesis, Schrödinger argued that chromosomes ‘contain in some kind of code-script the entire pattern of the individual’s future development and of its functioning in the mature state.’ This was the first time that anyone had clearly suggested that genes might contain, or even could simply be, a code.
    Taking his idea to its logical conclusion, Schrödinger argued that it should be possible to read the ‘code-script’ of an egg and know ‘whether the egg would develop, under suitable conditions, into a black cock or into a speckled hen, into a fly or a maize plant, a rhododendron, a beetle, a mouse or a woman.’ 46 Although this was partly an echo of the earliest ideas about how organisms develop and the old suggestion that the future organism was preformed in the egg, Schrödinger’s idea was very different. He was addressing the question of
how
the future organism was represented in the egg and the means by which that representation became biological reality, and suggesting these were one and the same:
    The chromosome structures are at the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power – or, to use another simile, they are architect’s plan and builder’s craft – in one.
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    To explain how his hypothetical code-script might work – it had to be extremely complicated because it involved ‘all the future development of the organism’ – Schrödinger resorted to some simple mathematics to show how the variety of different molecules found in an organism could be encoded. If each biological molecule were determined by a single 25-letter word composed of five different letters, there would be 372,529,029,846,191,405 different possible combinations – far greater than the number of known types of molecule found in any organism. Having shown the potential power of even a simple code, Schrödinger concluded that ‘it is no longer inconceivable that the miniature code should precisely correspond with a highly complicated and specified plan of development and should somehow contain the means to put it into operation.’ 48
    Although this was the first public suggestion that a gene contained something like a code, in 1892 the scientist Fritz Miescher had come up with something vaguely similar. In a private letter, Miescher had argued that the various forms of organic molecules were sufficient for ‘all the wealth and variety of hereditary transmission [to] find expression just as all the words and concepts of all languages can find expression in twenty-four to thirty alphabetic letters.’ 49 Miescher’s view can appear far-seeing, especially given that he was also the discoverer of DNA, or, as he called it, nuclein. But Miescher never argued that nuclein was the material making up these letters and his suggestion was not made public for nearly eighty years. Above all, the vague letter and word metaphor was nowhere near as precise as Schrödinger’s code-script concept.
    Schrödinger then explored what the gene-molecule might be made of and suggested that it was what he called a one-dimensional aperiodic crystal – a non-repetitive solid, with the lack of repetition being related to the existence of the code-script. The non-repetition provided the variety necessary to specify so many different molecules in an organism. Although Troland, Muller and Koltsov had all suggested two decades earlier that genes might grow like crystals, Schrödinger’s idea was far more precise. His vision of gene structure was focused on the non-repetitive nature of the code-script, rather than on the relatively simple parallel between the