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DNA Timeline (1928 Frederick Griffith (1944 Oswald Avery (1949 Erwin…
DNA Timeline
1928 Frederick Griffith
In 1928, Frederick Griffith was trying to make a vaccine for pneumonia. The nonvirulent bacteria was rough strained (R). The virulent bacteria was soft strained (S). Each bacteria was injected into a separate. The R strain bacteria injected mouse lived while the S strain bacteria injected mouse died. Next Griffith tried injecting heat-killed S bacteria into another mouse, that mouse lived. But, when the mouse was injected with an heat-killed S bacteria and R strain mixture, it died. Griffith had discovered a transformation that occurred within the R bacteria. It had a capsule that only the S bacteria has usually. This will lead to several scientists trying to understand why this happen
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1944 Oswald Avery
In 1944, Oswald Avery recreated Griffith's experiment.He used different kinds of enzymes that break down bacterial coats, proteins, RNA and DNA. The enzymes that broke down coats, proteins, and RNA still produced a virulent substance from the heat-killed S bacteria and R bacteria solution. The only one that didn't produce a virulent substance was the DNA killing enzymes. Oswald discovered that DNA was causing the transformation in the R bacteria
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1949 Erwin Chargaff
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Chargaff made the observation of that the adenine and thymine amounts were nearly equivalent. The amount of cytosine and guanine were also nearly equivalent. Chargaff made the discovery of the two classes of nitrogenous bases in DNA. Adenine and Thymine were consider a pair and Guanine and Cytosine were considered another pair
1952 Rosalind Franklin
By using X-Ray diffraction, (when x-ray beams are fired at an object and are scattered in a complex pattern on a sheet of film to determine the shape of a molecule) Franklin found that the structure of DNA truly is a double helix shape
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