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The History of DNA Structure Discovery

The History of DNA Structure Discovery. 1869 – Johann Miescher. Studied the nuclei of white blood cells Isolated the material using HCl ( aq ) and digestive proteins Named the substance nuclein Found the material was rich in nitrogen and phosphorus. 1919 – Pheobus Levene.

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The History of DNA Structure Discovery

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  1. The History of DNA Structure Discovery

  2. 1869 – Johann Miescher • Studied the nuclei of white blood cells • Isolated the material using HCl(aq) and digestive proteins • Named the substance nuclein • Found the material was rich in nitrogen and phosphorus

  3. 1919 – Pheobus Levene • Discovered that DNA was made up of chains of nucleotides NITROGEN RICH ACID RIBOSE

  4. 1920 – DNA vs Protein • thought that 4 nucleotides were connected in the same repeated pattern • protein have 20 amino acids which could be combined in many combinations

  5. Levene’s Nucleotide Pattern

  6. 1928 – Frederick Griffith • studied two strains of pneumococcus bacteria • rough strain = nonvirulent • injection into mouse did not result in death • smooth strain = virulent • injection caused mouse to die • http://www.youtube.com/watch?v=vQOdDGM5vSg

  7. Griffith’s Experiment

  8. Griffith’s Conclusions • some “factor” from the dead, virulent smooth strain “transformed” the living, non-virulent rough strain • non-virulent rough strain picked up DNA to become virulent

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

  10. Hammerling’s Experiment Hereditary information is stored in the nucleus. http://www.youtube.com/watch?v=tl5KkUnH6y0 no regrowth

  11. 1944 – Avery, McCarty & MacLeod • continued Griffith’s work with pneumococcus

  12. 1940s – Joshua Lederberg • demonstrated bacterial conjugation • bacteria can exchange DNA • bacteria have no nucleus or chromosomes • http://www.youtube.com/watch?v=7stZk6TesKk

  13. 1940s – Edwin Chargaff • for all organisms A = T and G = C Chargaff’s Rule • organisms with more Gs and Cs tend to be more complex

  14. 1952 – Hershey & Chase • conducted experiments to definitively show that DNA is the hereditary material • bacteriophage used to infect bacteria • bacterial virus • http://www.youtube.com/watch?v=3QJ4CjFsflA

  15. 1950s – Maurice Wilkins & Rosalind Franklin

  16. X-ray Crystallography • physics approach to examining biological molecules • https://www.youtube.com/watch?v=0tmNf6ec2kU Start at 14:35

  17. Rosalind Franklin’s X-rays The photo indicated: • Backbone of alternating phosphate and sugars • Backbone is a helical structure • Double helix structure (molecule is a uniform helix) • Nitrogenous bases are in the middle of the molecule • Bases are at right angles to the backbone

  18. Base Pairing • knew that each base could pair with itself

  19. 1953 – James Watson & Francis Crick • inspired by alpha-helix model of proteins • determined howA + T and G + C bonded together • width of purine + pyrimidine bonds fit perfectly between the sugar-phosphate backbone • the double helix model offered an easy method for replication

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