3. Erwin Chargaff discovered a key piece of information when analysing DNA from a wide range of species.He found that in every case, the proportions of cytosine and guanine were the same. He found the same for the proportions of adenine and thymine. There was no relationship between other combination of bases. Linus Pauling showed that polypeptide chains are often held in the shape of an α-helix by hydrogen bonds that could be broken by moderate heating.He suggested a similar helical structure might explain changes that had been seen on DNA when it's heated. Maurice Wilkins and Rosalind Franklin were working on the X-Ray diffraction of DNA. It was hard to get pure crystals of DNA to work with, and the pictures were very complicated to interpret. Wilkins and Franklins were supposed to work together, but an intense rivalry developed between them. While Franklin developed methods of obtaining high quality X-ray diffraction pictures of the DNA molecule, James Watson and Francis Crick were try a different approach. They gathered all the available information about DNA and kept trying to build a model that fitted with all the facts. They worked with space-filling models and also with simpler representations of the known components of DNA. Any model they produced had to explain all the available data about the structure of the molecule and how it behaved. By getting information from other researchers and manipulating models, an idea emerged which seemed to work. Wilkins passed them detailed measurements Franklin had obtained, without her permission. This gave them the final evidence they needed to confirm their ideas without ever carrying out an experiment.What they found was the double helix. The patterns on the X-ray suggested a helix measuring 3.4nm or every complete turn. Watson noticed that if in every case cytosine was paired with guanine, and thymine with adenine, hydrogen bonds would hold them together. The two sets of base pairs are roughly the same size and they fit witihin the measured dimensions of the molecule.
... That's not even finished... I can't be bothered to add more.
Such typical high school plays.
