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The History of DNA

The History of DNA. Page 273-278 Page 279 Questions 1, 2, 4, 8. 1920 – What is the heredity molecule?. Importance of Mendel’s work. Scientists were mostly sure that proteins were the genetic material Why not DNA?. Nucleotide Pattern. 1920 – What is the heredity molecule?.

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The History of DNA

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  1. The History of DNA Page 273-278 Page 279 Questions 1, 2, 4, 8

  2. 1920 – What is the heredity molecule? • Importance of Mendel’s work. • Scientists were mostly sure that proteins were the genetic material • Why not DNA?

  3. Nucleotide Pattern

  4. 1920 – What is the heredity molecule? • Importance of Mendel’s work. • Scientists were mostly sure that proteins were the genetic material • Why not DNA? • Why did they think it was proteins?

  5. 1928 – Frederick Griffith Studied two strains of Pneumococcusbacteria • rough R-strain = non-virulent • smooth S-strain = virulent

  6. Griffith’s Experiment

  7. Griffith Experiment Conclusions Some “factor” from the dead, virulent smooth strain “transformed” the living, non-virulent rough strain. What was their conclusion?

  8. nucleus at bottom of stalk 1930 – Joachim Hammerling Acetabularia– type of alga

  9. Hammerling’sExperiment #1 no regrowth

  10. Hammerling’s Experiment #2 What was his conclusion?

  11. 1944 – Avery, McCarty & MacLeod Continued Griffith’s work with virulent Pneumococcus Tested three conditions: • s strain + protease • s strain + RNase • s strain + DNase

  12. Avery, McCarty & MacLeod Experiment Conclusion What do the results of this experiment mean?

  13. 1940s – Edwin Chargaff Studied concentrations for each of the four nucleotides. Chargaff’s Rule? Question that will be on the quest: Why are organisms with a higher percentage of G’s and C’s generally more complex?

  14. 1952 – Hershey & Chase Studied bacteriophage (a bacterial virus) used to infect bacteria

  15. Hershey & Chase Hershey & Chase Experiment

  16. 1950s – Maurice Wilkins & Rosalind Franklin

  17. X-ray Crystallography Physics approach to examining biological molecules. A pure sample of the molecule is isolated. X-rays bombard the sample and refract the rays in multiple directions.

  18. X-ray Crystallography

  19. Rosalind Franklin’s X-rays The photo indicated:

  20. DNA Structure

  21. What’s Left to Discover? Hereditary molecule is DNA. DNA molecules are polynucleotides. DNA has a double-helix structure with alternating sugar-phosphate molecules. How are the bases arranged in the middle?

  22. 1953 – James Watson & Francis Crick

  23. 1953 – James Watson & Francis Crick Inspired by alpha-helix model of proteins. Determined howA + T and G + C bonded together.

  24. Base Pairing

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