What Rosalind Franklin contributed to the discovery of DNA’s structure
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Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#2> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance.
That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA through a combination of going on daily walks, playing with models, and taking LSD.
It is Linus Pauling who would have been able to instantly figure out the structure of DNA by glancing at Photograph 51. His initial theory had been that the phosphates were on the inside of the structure, which in hindsight would never work because the negative charges would repel each other.
Source: Don't remember the primary source, but we covered it in Martin Stranathan's AP Bio class in high school
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#3> Lore has it that the decisive insight for the double helix came when Watson was shown an X-ray image of DNA taken by Franklin — without her permission or knowledge. Known as Photograph 51, this image is treated as the philosopher’s stone of molecular biology, the key to the ‘secret of life’ (not to mention a Nobel prize). In this telling, Franklin, who died of ovarian cancer in 1958 at just 37, is portrayed as a brilliant scientist, but one who was ultimately unable to decipher what her own data were telling her about DNA. She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance.
I don't think this is what Watson wrote in The Double Helix. He wrote that Crick, with his background in math and physics, could understand the image produced by Franklin but that he -- Watson -- could not.
Watson does write that Franklin thought DNA wasn't helical. The linked article provides an interesting explanation for why she thought that (at least at one time). As far as I can tell, that backs up Watson's narrative rather than undermining it.
One interesting takeaway from The Double Helix was that Watson and Crick cracked the problem with guess-and-check model building (the article mentions this). Sure, they had some vague idea that DNA was a helix and that A-T, C-G relatinoship, but they basically played with tinker toys until they got something that looked good. Watson claims that they decided on a double helix because of his intuition that "in biology, important things occur in pairs".
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#4> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
Nice shout out to your teacher!
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#5My favorite candidate for 'getting cheated for credit' on the DNA discovery is Erwin Chargaff, whose work pointed towards the specific base pairing involved. Of course, the arbitrary 3-person cutoff for Nobel Prizes is not at all reflective of how science is done in practice in terms of the numbers of people involved over time in any major discovery:
> "Key conclusions from Erwin Chargaff's work are now known as Chargaff's rules. The first and best known achievement was to show that in natural DNA the number of guanine units equals the number of cytosine units and the number of adenine units equals the number of thymine units."
> "The second of Chargaff's rules is that the composition of DNA varies from one species to another, in particular in the relative amounts of A, G, T, and C bases. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein."
https://en.wikipedia.org/wiki/Erwin_Chargaff#Chargaff's_rule...
Not to distract from Rosalind Franklin's contributions, but if anyone is looking for a female role model in molecular biology and biochemistry with a major influence and a long career, Barbara McClintock is probably at or near the top of that list:
https://www.nature.com/scitable/topicpage/barbara-mcclintock...
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#6> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
As I learned it, Photograph 51 was so good that anybody with any crystallography experience would have been able to tell the structure at a glance. Exactly, like you said she wanted to sit on it and get more data because, allegedly, she had observed Hoogsteen base pairing, or some other non-canonical base pair that escapes me.
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#7> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
As I learned it, Photograph 51 was so good that anybody with any crystallography experience would have been able to tell the structure at a glance. Exactly, like you said she wanted to sit on it and get more data because, allegedly, she had observed Hoogsteen base pairing, or some other non-canonical base pair that escapes me.
Today, sure. It's famous.
But as https://www.tandfonline.com/doi/pdf/10.1080/1464518031000160... points out, the analysis technique that makes it possible to deduce the structure from the image was first developed 2 years earlier in a paper by Crick, Cochran and Vand. Note the lead author. In 1953, Francis Crick was one of a handful of people on the planet who would have made the connection. In fact he was able to make it from James Watson's description of the photograph! Rosalind Franklin can be pardoned for having failed to make the connection.
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#8> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
Linus Pauling may have been the better chemist, but Francis Crick was better prepared to figure out the structure from that particular photograph.
The necessary analysis technique was first developed 2 years earlier, in a paper that Crick was the lead author on. Chance favors the prepared mind. And Crick was extremely well-prepared for this task.
Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#9> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
Nice shout out to your teacher!
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Re: What Rosalind Franklin contributed to the discovery of DNA’s structure
#10> She supposedly sat on the image for months without realizing its significance, only for Watson to understand it at a glance. That's not the lore as I learned it. The lore is that Franklin sat on the data for months before analyzing it (she wanted to collect more data). Then W+C visited her lab and saw the data, but did not instantly understand it. Instead, the lore is that they figured out the structure of the DNA…
didn't pauling think that dna was a triple helix? how this could of worked i have never understood.