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The Discovery of DNA

The Discovery of DNA. GREGOR MENDEL. 1847 Austrian monk who worked with pea plants to study genetic inheritance “Father of Genetics” Discovered ‘factors’ are passed down from parent to offspring *Did NOT know what DNA was or that it was the genetic material. FREDERICK GRIFFITH. 1928

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The Discovery of DNA

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  1. The Discovery of DNA

  2. GREGOR MENDEL • 1847 • Austrian monk who worked with pea plants to study genetic inheritance • “Father of Genetics” • Discovered ‘factors’ are passed down from parent to offspring *Did NOT know what DNA was or that it was the genetic material

  3. FREDERICK GRIFFITH • 1928 • Griffith's experiment involved mice and two types of pneumonia, a virulent (S) and non-virulent kind (R). • S = smooth coated bacteria • R = rough (no coating) bacteria • EXPERIMENT: • Injected live S = mouse died • Injected live R = mouse lived • Injected heat killed S = mouse lived • Injected heat killed S + live R = mouse died • Cells inside dead mouse had S bacteria • CONCLUSION * genetic material must have been transferred from heat killed S bacteria to live R bacteria  changed harmless R bacteria into deadly S bacteria = “transformation principle”

  4. OSWALD AVERY • 1942 • Continued Griffith’s experiment to see what the genetic material was that was being passed on. • Experiment - he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia.  Transformation still occurred. • Next he destroyed the deoxyribonucleic acid.  Transformation did not occur.  DNA must be inherited material

  5. NOW THAT WE KNOW DNA IS THE GENETIC MATERIAL… WHAT IS IT’S STRUCTURE?

  6. HERSHEY AND CHASE • 1952 • Proteins or DNA = genetic material? • Worked with bacteriophage: • Infects bacteria cells • Composed of protein coat with DNA inside • Used radioactive isotopes to “tag” DNA and proteins • Helped confirm DNA is genetic material

  7. ERWIN CHARGAFF • 1940S • noticed a pattern in the amounts of the four bases: adenine, guanine, cytosine, and thymine. • took samples of DNA of different cells and found that the amount of adenine = amount of thymine, and that the amount of guanine = equal the amount of cytosine.  • CHARGAFF’S RULE: A=T and G=C

  8. ROSALIND FRANKLIN • 1952 • Decided to try to make a crystal of the DNA moleculeto obtain an x-ray of it • They were successful  x-ray crystallography image of DNA • The image appeared to contain rungs, like those on a ladder between to strands that are side by side.  • It showed DNA had a (X) helix shape.

  9. WATSON AND CRICK • 1953 • Co-discoverers of the structure of DNA • Used x-ray diffraction images from Rosalind Franklin and proposed the double helix structure of DNA • Built the first 3D model of DNA

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