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History of The discovery of DNA

History of The discovery of DNA. Johann Friedrich Mieschner 1869. Mieschner discovered large molecules in the nucleus of the cell that were acidic . He called them nucleic acids. He didn’t know what they were for. Frederick Griffith 1928. 8 0 years later

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History of The discovery of DNA

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  1. History of The discovery of DNA

  2. Johann Friedrich Mieschner1869 Mieschner discovered large molecules in the nucleus of the cell that were acidic . He called them nucleic acids. He didn’t know what they were for.

  3. Frederick Griffith1928 • 80 years later • Bacteria could share “genetic material”. • It could transfer from 1 bacteria to another

  4. Griffith’s Experiment

  5. Frederick Griffith’s experiment • There were 2 kinds of Pneumonococcusbacteria • Rough strain was harmless to the mice. • Smooth strain killed the mice. • If he heat killed the smooth strain then the mice lived. • If he mixed the heat killed smooth bacteria with the rough strain, then the mice died. • Something was transferred from the dead bacteria into the live innocuous bacteria that made it deadly. .

  6. Oswald Avery and coworkers Colin McCleod and Maclyn McCarty1944 • Common belief was protein carried the genetic information. • Avery removed all the protein from the bacteria and repeated the Griffith experiment. It still transformed the Bacteria • DNA was the “something” that carried the genetic information

  7. Linus Pauling1950 • Protein chains were helical. The first twist is called the alpha helix. • The 2nd twist is the beta sheets • DNA was similar also helical. • He won 2 Nobel prizes 1 in chemistry for protein structure. • Nobel peace prize for his work vs. above ground nuclear testing.

  8. Rosalind Franklin1951 • She perfected the technique of x-ray chrystalography • Took the first photographs of DNA • Identified 2 kinds • Her unpublished papers inspired and supported Watson and Crick. • Personality clashes with her collegue Wilkins, prevented her from getting credit.

  9. Erwin Chargaff1951 • 2 rules • Using paper chromatography he found the amount of adenine = thiame • And the amount of cytosine = guanine • Different species had different ratios of nitrogen bases.

  10. James Watson and Francis Crick1953 • Discovered the double helix structure of DNA. • Twisted ladder (Left handed twist) • Sugar phosphates sides (anti parallel) • Nitrogen bases for rungs (Complimentary) • As you can see they stood on the support of their collegues. • Won the Nobel Prize 1962 with Maurice Wilkins. Rosalind Franklin was not included

  11. Matthew Messelson and Franklin W. Stahl1958 • Determined the method by which DNA replicated. • If it was the “Stuff of inhertance” it had to duplicate. • One new strand and one old strand (Semi conservative)

  12. Crick and coworkers1961 • The triplicate code • Three DNA nucleotides code for 1 amino acid Nirenberg and coworkers 1964 • Supported Crick’s hypothesis

  13. Human Genome Project2003 • identify all the approximately 20,000-25,000 genes in human DNA, • determine the sequences of the 3 billion chemical base pairs that make up human DNA, • 1993 NIH & Dept of Energy joined to become the National Human Genome Research Institute (NHGRI) Headed by Francis Collins. • 1998 Craig Venter and Celera Genomics wanted to do it privately and get patents for the genes. • This was deemed unethical in 2000 but the competition speeded up the process

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