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History of DNA

History of DNA. How it Was Discovered. Friedrich Miescher 1869 (Germany). Isolated deoxyribonucleic acid from nucleus of cells Called this white, slightly acidic chemical “ nuclein ” Didn’t know it was genetic material. Frederick Griffith 1928 (England).

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History of DNA

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  1. History of DNA How it Was Discovered

  2. Friedrich Miescher 1869 (Germany) • Isolated deoxyribonucleic acid from nucleus of cells • Called this white, slightly acidic chemical “nuclein” • Didn’t know it was genetic material

  3. Frederick Griffith 1928 (England) • Working on vaccine for pneumonia bacteria • Discovered that by killing inside of bacteria, it wouldn’t give disease to mice

  4. Many Scientists 1940 • By this time, many scientists isolated all of the chemicals found in DNA • Phosphate (PO4) • Sugar (deoxyribose) • Four nitrogen bases (adenine, thymine, cytosine, guanine) • Now called “deoxyribose nucleic acid” or DNA

  5. Oswald Avery 1944 (USA) • Worked with bacteria that causes pneumonia • Used DNA-destroying enzyme to destroy DNA inside bacteria before inserting it into animal • Animal didn’t get pneumonia • DNA is genetic material

  6. Erwin Chargaff 1950 (USA) • Biochemist who discovered that ratio of adenine to thymine was always 1:1 and the ratio of cytosine to guanine was always 1:1 in ALL living organisms • In human DNA, for example, the four bases are present in these percentages: A=30.9% and T=29.4%; G=19.9% and C=19.8% • Termed “Chargaff’s Rules” A = 30% G = 20% C = 20% T = 30%

  7. Rosalind Franklin 1951 (England) • Worked on x-ray crystal diffraction photographs (how light bounced off crystals) of DNA structure • Worked in same area as Maurice Wilkins who tended to treat her as his assistant • Wilkins was working on separate DNA projects

  8. Structure • … was still unknown • How did the phosphate, deoxyribose, and 4 nitrogenous bases fit together?

  9. James Watson and Francis Crick, 1953 (England) • Wilkins showed Watson Dr. Franklin’s x-ray photograph without her permission • Watson said "The instant I saw the picture, my mouth fell open and my pulse began to race.” • Showed photo to Crick who instantly began work with Watson on DNA model using balls and sticks • 1953 scientific paper published called “A Structure for Deoxyribose Nucleic Acid”

  10. Nobel Prize 1962 • Maurice Wilkins,Francis Crick, and James Watson received Nobel Prizes for Physiology or Medicine for work on DNA structure • Rosalind Franklin died 4 yrs earlier in 1958 at age 37 of ovarian cancer • Nobel prizes are only given to living persons so she will never be honored

  11. MOVIE – SECRET OF PHOTO 51 • Meet the unsung heroine behind the discovery of DNA’s double helix. Rosalind Franklin 1920-1958

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