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02b   history of dna
02b   history of dna
02b   history of dna
02b   history of dna
02b   history of dna
02b   history of dna
02b   history of dna
02b   history of dna
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02b history of dna

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  • 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>
  • 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>
  • 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>
  • 6. 1950s – Maurice Wilkins & Rosalind Franklin
  • 7. X-ray Crystallography <ul><li>physics approach to examining biological molecules </li></ul>
  • 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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