Maurice Wilkins, Rosalind Franklin, And Linus Pauling

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James Watson and Francis Crick utilized the work and evidence of many different scientists in order to come to their final conclusion as to the structure of DNA; greatly using the work of Maurice Wilkins, Rosalind Franklin, and Linus Pauling.
The first time Watson is truly introduced to the world of X-ray diffraction pictures of DNA was when attending a lecture held by Wilkins. From this, he learns that genes are able to crystallize, so they therefore must have a regular and repeating structure (33). After having Pauling’s model for polypeptides described to him, Watson initially thought that DNA would be found to be an alpha helix, meaning that there would only be one peptide chain holding it together. However, it was soon determined that …show more content…

Crick and Cochran both completed calculations for the mathematics of the DNA structure, and by confirming their calculations, determined that both Linus’ model for polypeptides and their theory were correct (66-67). Then, with that information, Crick concluded that there were only a small number of solutions that lined up with both the Cochran-Crick theory and Rosy’s data. In knowing that the X-ray data showed that there was 2, 3, or 4 polynucleotide chains, they then only had to determine the angle and radius of the DNA strand (77). Further evidence showed that the backbone of DNA had to be sugar-phosphate in order to produce the crystalline diffraction patterns seen by Maurice and Rosy, and confirmed that there must be more than one chain in DNA due to the forces which were holding the chains together (80)(88). Then having to shift their focus to other work while secretly still aiding in their hunt for the structure of DNA, the used evidence of bacterial infection in a phage being caused by the injection of viral DNA, which was found via phage …show more content…

With the knowledge of J.M. Gulland and D. O. Jordan’s papers on acid base titrations of DNA, Watson knew that bases form hydrogen bonds to other hydrogens, and that these bonds were present in DNA (183). Watson then thought that DNA had 2 chains with identical base sequences held together with hydrogen bonds, but struggled with figuring out if replication would work perfectly indefinitely, as the wrong bases could bind together (184-188). However, this model was soon found to be incorrect, as thymine and guanine were in enol form in Watson’s model, but should have actually been in keto form (190). Then, with this error found, Watson began rearranging the bases within DNA to see if there were any formations that would not disrupt the structure of the polynucleotide chains as previous models had. After rearranging the bases, Watson discovered that A+T pairs with 2 hydrogen bonds and C+G pairs with at least 2 hydrogen bonds were the same shape, and thus did not bend the chains in a way that was not mathematically possible.

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