demonstrated. Nevertheless, as time wore on, there were fewer reasons not to accept Avery’s findings.
Some scientists had strong personal reasons to reject the DNA hypothesis. Mirsky’s career was based on the study of nucleoproteins and he was clearly not going to give up his world view without a fight. Through his articles, his lectures and his interventions at conferences, Mirsky sowed doubt among the undecided. Similarly, Wendell Stanley turned a blind eye to the work of the Avery group, even though he too had been familiar with it before publication. In 1936, Stanley had crystallised the tobacco mosaic virus and announced that it was a protein; this was finally shown to be wrong in 1956 – the hereditary material in this virus is in fact RNA, and small amounts of RNA in his protein extract accounted for his results. In 1946, Stanley won the Nobel Prize in Physiology or Medicine for his mistaken claim; he later said that he ‘was not impressed’ by Avery’s discovery – otherwise he would have immediately tested tobacco mosaic virus RNA for specificity. In 1970, he concluded, somewhat shamefacedly:
I have searched my memory and have failed to find any really extenuating circumstances for my failure to recognize the full significance of the discovery of transforming DNA.
43
The diffident response of the main members of the phage group – Delbrück, Luria and Hershey – had a rather different source, and all three of them later explained their behaviour in the same way: they were interested in genetics, not chemistry, and so they simply did not realise the potential implications. Typically robust, Delbrück said:
And even when people began to believe it might be DNA, that wasn’t really so fundamentally a new story, because it just meant that genetic specificity was carried by some goddamn other macromolecule, instead of proteins.
44
Luria recalled: ‘I don’t think we attached great importance to whether the gene was protein or nucleic acid. The important thing for us was that the gene had the characteristics that it had to have.’ 45 In 1994, Hershey explained that their focus was simply elsewhere – ‘as long as you’re thinking about inheritance, who gives a damn what the substance is – it’s irrelevant.’ 46 Ironically, Hershey is now best known for his attempt to resolve the issue of whether proteins or DNA are the basis of heredity, an experiment that students are now taught settled the question once and for all, even though it did not.
*
Alfred (‘Al’) Hershey was a tall, skinny taciturn man with a toothbrush moustache and bad teeth. Although he was renowned for working long into the night, he was not solely focused on science – he often took afternoon naps and in the summer he would disappear for weeks on end, sailing his yacht on Lake Michigan. Like everyone else in the phage group, Hershey had followed the discussions around the chemical nature of Avery’s transforming principle. In May 1949, Hotchkiss sent Hershey an update on his progress in excluding any possible protein contamination from the DNA extracts of the transforming principle; after looking at the data, Hershey wrote to the younger man: ‘The experiments are very beautiful. … My own feeling is that you have cleared up most of the doubts.’ 47 But like Luria and Delbrück, Hershey’s initial interest in Avery’s experiments was unfocused – the members of the phage group could not see how chemistry could help them understand genetics.
Nevertheless, as phage researchers tried to understand how viruses reproduced, the question of chemistry became increasingly pressing. By 1949, electron microscope images had shown that a viral infection begins with the virus sitting on the outside of a cell; in ways that were unclear, the virus then took over the cell’s metabolic system and ‘lost its identity’ – no viruses could be detected inside the cell for a period, while the viral structures that were still on the
Some scientists had strong personal reasons to reject the DNA hypothesis. Mirsky’s career was based on the study of nucleoproteins and he was clearly not going to give up his world view without a fight. Through his articles, his lectures and his interventions at conferences, Mirsky sowed doubt among the undecided. Similarly, Wendell Stanley turned a blind eye to the work of the Avery group, even though he too had been familiar with it before publication. In 1936, Stanley had crystallised the tobacco mosaic virus and announced that it was a protein; this was finally shown to be wrong in 1956 – the hereditary material in this virus is in fact RNA, and small amounts of RNA in his protein extract accounted for his results. In 1946, Stanley won the Nobel Prize in Physiology or Medicine for his mistaken claim; he later said that he ‘was not impressed’ by Avery’s discovery – otherwise he would have immediately tested tobacco mosaic virus RNA for specificity. In 1970, he concluded, somewhat shamefacedly:
I have searched my memory and have failed to find any really extenuating circumstances for my failure to recognize the full significance of the discovery of transforming DNA.
43
The diffident response of the main members of the phage group – Delbrück, Luria and Hershey – had a rather different source, and all three of them later explained their behaviour in the same way: they were interested in genetics, not chemistry, and so they simply did not realise the potential implications. Typically robust, Delbrück said:
And even when people began to believe it might be DNA, that wasn’t really so fundamentally a new story, because it just meant that genetic specificity was carried by some goddamn other macromolecule, instead of proteins.
44
Luria recalled: ‘I don’t think we attached great importance to whether the gene was protein or nucleic acid. The important thing for us was that the gene had the characteristics that it had to have.’ 45 In 1994, Hershey explained that their focus was simply elsewhere – ‘as long as you’re thinking about inheritance, who gives a damn what the substance is – it’s irrelevant.’ 46 Ironically, Hershey is now best known for his attempt to resolve the issue of whether proteins or DNA are the basis of heredity, an experiment that students are now taught settled the question once and for all, even though it did not.
*
Alfred (‘Al’) Hershey was a tall, skinny taciturn man with a toothbrush moustache and bad teeth. Although he was renowned for working long into the night, he was not solely focused on science – he often took afternoon naps and in the summer he would disappear for weeks on end, sailing his yacht on Lake Michigan. Like everyone else in the phage group, Hershey had followed the discussions around the chemical nature of Avery’s transforming principle. In May 1949, Hotchkiss sent Hershey an update on his progress in excluding any possible protein contamination from the DNA extracts of the transforming principle; after looking at the data, Hershey wrote to the younger man: ‘The experiments are very beautiful. … My own feeling is that you have cleared up most of the doubts.’ 47 But like Luria and Delbrück, Hershey’s initial interest in Avery’s experiments was unfocused – the members of the phage group could not see how chemistry could help them understand genetics.
Nevertheless, as phage researchers tried to understand how viruses reproduced, the question of chemistry became increasingly pressing. By 1949, electron microscope images had shown that a viral infection begins with the virus sitting on the outside of a cell; in ways that were unclear, the virus then took over the cell’s metabolic system and ‘lost its identity’ – no viruses could be detected inside the cell for a period, while the viral structures that were still on the
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