Free Life's Greatest Secret by Matthew Cobb Page B

electrophoresis and ultraviolet radiation were all identical to those of DNA. Every result converged on the same conclusion: the transforming principle was composed of DNA.
    The discussion section of the article outlined the genetic context of their findings, using similar terms to their Rockefeller Institute report from earlier in the year:
    The inducing substance has been likened to a gene, and the capsular antigen which is produced in response to it has been regarded as a gene product.
    Furthermore, the potential links of transformation with ‘similar problems in the fields of genetics, virology, and cancer research’ were indicated, clearly outlining the implications of their discovery. And yet, despite the overwhelming evidence, all of which suggested that the transforming principle was made of DNA and that genes might be, too, the final paragraph of the article opened with a phrase that suggested the team were not quite as confident as they ought to have been:
    It is, of course, possible that the biological activity of the substance described here is not an inherent property of the nucleic acid but is due to minute amounts of some other substance adsorbed to it or so intimately associated with it as to escape detection.
    Despite the fact that this deflating phrase was immediately followed by a set of counter-arguments, the tone tended to undermine the reader’s confidence. Even the final bold sentence introduced doubt where none was needed:
    If the results of the present study on the chemical nature of the transforming principle are confirmed, then nucleic acids must be regarded as possessing biological specificity the chemical basis of which is as yet undetermined.
    19
    On 1 November, Avery handed the manuscript to his colleague Peyton Rous, who was the editor of the
Journal of Experimental Medicine,
which was published by the Rockefeller Institute. Rous did not send the article out for other scientists to review before publication – that was not the general practice at the time – but instead made some editorial suggestions, including cutting what he considered to be a speculative passage about the role of nucleic acids. 20 And with that the article was accepted.
    On 10 December 1943, Avery presented the findings at the regular Friday afternoon Rockefeller Institute staff meeting – the first time in years that he had talked about the work of his group. After Avery spoke there was a warm round of applause, followed by a deafening silence. There were no questions. Eventually Dr Heidelberger of Columbia University rose and emphasised the many years that Avery had been working on the problem. Then he sat down again and another silence ensued. The meeting was then closed. Avery had described one of the most momentous discoveries in the history of science, and no one could think of anything to say.
    *
    The article appeared in the 1 February 1944 issue of the
Journal of Experimental Medicine,
but Avery’s work was not over. As the concluding part of the paper indicated, Avery and McCarty feared that the evidence would not convince the majority of scientists who thought that genes were made of proteins. Even if all the protein-removing procedures were working at their best, molecules are so tiny that even in the smallest amount of ‘pure’ extract that worked in their system – a mere 0.003 micrograms, or 0.00000003 grams – there could still be millions of protein molecules in the sample, each of which might correspond to a gene. The biochemical and analytical techniques available at the time meant that it was not possible to confidently remove that final portion of protein, or to prove that a sample was completely protein-free. So in 1944 Avery and McCarty tried to attack the problem from the other side by showing that even minute quantities of an enzyme that attacked DNA would stop transformation. Both men began to feel the strain. Avery became increasingly withdrawn and even depressed as he tried to find