02b history of dna

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02b history of dna

  1. 1. 1952 – Hershey & Chase <ul><li>conducted experiments to definitively show that DNA is the hereditary material </li></ul><ul><li>bacteriophage used to infect bacteria </li></ul><ul><ul><li>bacterial virus </li></ul></ul>
  2. 3. Hersey & Chase <ul><li>What they knew: </li></ul><ul><ul><li>Virus are composed of DNA and protein </li></ul></ul><ul><ul><li>Virus infection reprograms a host cell to produce more virus </li></ul></ul><ul><li>Question: which viral component is responsible for the reprogramming, DNA or protein? </li></ul>
  3. 4. Hersey & Chase <ul><li>Bacteriophage / phage: virus that infects bacteria </li></ul><ul><li>Radioactive sulfur which labels proteins </li></ul><ul><li>Radioactive phosphorus which labels DNA </li></ul>
  4. 5. Hersey & Chase <ul><li>Virus injects DNA into host cell during infection, protein stays outside </li></ul><ul><li>DNA provides information to reprogram host cells to make more virus </li></ul><ul><li>In virus, DNA is the hereditary material, not proteins </li></ul><ul><li>Video: Website </li></ul><ul><li>http://highered.mcgraw-hill.com/olc/dl/120076/bio21.swf </li></ul>
  5. 6. 1950s – Maurice Wilkins & Rosalind Franklin
  6. 7. X-ray Crystallography <ul><li>physics approach to examining biological molecules </li></ul>
  7. 8. Rosalind Franklin’s X-rays <ul><li>The photo indicated: </li></ul><ul><li>Backbone of alternating phosphate and sugars </li></ul><ul><li>Backbone is a helical structure </li></ul><ul><li>Double helix structure (molecule is a uniform helix) </li></ul><ul><li>Nitrogenous bases are in the middle of the molecule </li></ul><ul><li>Bases are at right angles to the backbone </li></ul>

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