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| 1869 he took pus samples from hospital and isolated pus by sprinkling salt on bandages, then got nuclei out by using alkaline then he isolated nuclein from the nuclei he found that nuclein was in every cell, nuclein is nucleic acid which is important in making amino acids for proteins |
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| 1950He thought there was more to DNA then the tetranucleoid shape that was proposed and he measured at adenine thyminet guanine and cytosine in many different cells from different organisms he found out that a and t had relatively the same number and g and c had relatively the same number he thought that tetranucleoid shape wouldnt work because numbers werent same foratgc |
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| Rosalind Franklin/Maurice Wilkins |
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| 1951 Rosalind franklin took xray crstallograph pictures of dna fibre which showed the helix shape which allowed James Watson and Francis Crick to solve the shape |
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| 1952 , Proposeda triple helix shape where phosphate faces inwards and nitrogen bases facing outwards but this was wrong because phosphate has negative oxygens which would repel each other |
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| 1952 they proved dna was genetic material by making bacterial viruses (phages) in the presence of radioactive sulphur which became a part of protein shell then when it infected host bacteria it stayed on outside, then they used radio active phosphorus and when phage infected bacteria dna went inside and replicated |
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| James Watson and Francis Crick |
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| 1953 they used rosalind wranklin and maurice wilkins pictures to prove the shape they found out that in each helical repeat there were 10 nucleotides becuase distance between stacked pairs was 3.4 anstroms and each helical repeat was 34 angstroms, the x in the diagram meant it was a helix, with phosphate groups facing outwards and bases inwards, at and gc were same size this allowed them to be stacked on top of each other keeping the helix shape which was antiparallel |
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