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Unlocking DNA: The Blueprint of Life

Explore the discovery and structure of DNA - the genetic blueprint of life. From its humble beginnings to the groundbreaking models by Watson and Crick, learn the key points that shaped our understanding of this fundamental molecule. Create your own DNA model to visualize its structure and functions. Delve into the fascinating history and significance of DNA in this informative journey through science.

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Unlocking DNA: The Blueprint of Life

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  1. DeoxyriboNucleic Acid The Blueprint of Life

  2. Who discovered DNA? • Swiss chemist Friedrich Miester in 1869 • Nobody cared

  3. Assumption of the Time • Proteins were well-known and assumed to be the genetic carrier • Lots of different proteins discovered, 20 different amino acids

  4. Phoebus Levene (1910s) • Russian biochemist who studied DNA, or nuclein as it was originally called • Discovered structure of nucleotides and • the presence of 4 unique DNA nucleotides

  5. Nucleotide Structure

  6. How Did We Determine DNA was the Genetic Material? • Two major sets of experiments conducted over 20-30 years • Avery, MacLeod and McCarty (1944) • Hershey and Chase (1952)

  7. Avery, MacLeod, McCarty • Tried to explain the findings of Frederick Griffith in 1928

  8. Griffith’s Experiment • Passage of a substance could transform harmless bacteria into deadly virulent bacteria

  9. Avery, MacLeod + Griffith • Demonstrated that transformation occurred when proteins were removed • Transformations did not occur when DNA was removed • Thus it was the DNA responsible for transforming a bacteria

  10. Avery, MacLeod and McCarty

  11. Alfred Hershey and Martha Chase • Tried to explain how bacteriophages invaded bacteria and changed their behavior • It was known that bacteriophages consisted of proteins and DNA

  12. Results of Hershey Chase

  13. Erwin Chargaff • Species differed in the number of each nucleotide they contained • The number of As and Ts was usually similar, same with Gs and Cs

  14. Rosalind Franklin and Maurice Wilkins • Used a technique called X-Ray Crystallography to study shape

  15. The X-Ray Image • Demonstrated that the shape of DNA was a double helix, with the nitrogenous bases on the inside • She independently discovered the structure of DNA

  16. They Did Her Dirty • Her X-Ray image was shown to other scientists (including Watson and Crick) without her permission • Watson and Crick used the X-Ray and some of Franklin’s earlier work to suggest the double helix model of DNA • She died at 37 so we’ll never know if she would have shared in their Nobel Prize 

  17. James Watson and Francis Crick

  18. Watson and Crick • Published their model in a 1 page paper • Literally had made models out of cardboard until one fit

  19. Key Points in the Model • DNA is double stranded in a double helix • Strands are held together by H-bonds between nitrogenous bases • A-T 2 hydrogen bonds • G-C 3 Hydrogen bonds • Backbone is made up of alternating sugar and phosphate • DNA strands are anti-parallel (run in opposite directions)

  20. DNA Model • Working in groups you will design and build a simple model of DNA • It should demonstrate the 4 key points of the Watson/Crick model • Can be made out of anything. Should have something representing Phosphate, Sugar, each of the 4 bases and H-bonds (the correct number) • Due Monday

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