KEY SCIENTISTS INVOLVED

1. The discovery of DNA Double Helix is one of the greatest findings of all time, but it’s also one of the most controversial

2. KEY SCIENTISTS INVOLVED

3. James Watson Francis Crick Rosalind Franklin Maurice Wilkins

4. What is DNA?

5. DNA (Deoxyribonucleic Acid) DNA is a double stranded molecule that is twisted into a Helix (Spiraling Staircase) DNA Double Helix

6. Each strand consists of: 1)A Sugar Phosphate Backbone

7. Each strand consists of: 1) A Sugar Phosphate Backbone 2) Four Base Chemicals (Attached in Pairs)

8. 1. Long Search: The search for the secret of life dates back nearly a century prior to Watson and Crick’s ground breaking discovery in 1953 1865 1909 1911 1929 1944 1950

9. The Early Efforts Gregor Mendel: Introduces the concept of heredity 1865 1909 1911 1929 1944 1950

10. The Early Efforts Wilhelm Johannsen: Coins the term “Gene” 1865 1909 1911 1929 1944 1950

11. The Early Efforts Thomas Hunt Morgan: Discovers that genes are responsible for inheritance 1865 1909 1911 1929 1944 1950

12. The Early Efforts Phoebus Levene: Discovers that DNA is made up of nucleotides, phosphates, sugars and 4 bases 1865 1909 1911 1929 1944 1950

13. The Early Efforts Oswald Avery: Shows that DNA can transform the property of cells However, this idea was not universally accepted 1865 1909 1911 1929 1944 1950

14. The Early Efforts Erwin Chargaff: Shows that: A + G = T + C = 50% Chargaff’s Rule is an important equation in the discovery of the structure of DNA 1865 1909 1911 1929 1944 1950

15. Background

16. Soon after WWII the race to discover the “Secret of Life” was on. Scientists knew this would be the discovery of the century and would guarantee a Nobel Prize.

17. Cambridge University Caltech University James Watson Francis Crick King’s College Linus Pauling Rosalind Franklin Maurice Wilkins VS

18. King’s College Franklin Wilkins King’s College • Rosalind Franklin accepts a job at King’s College to work in Maurice Wilkins’ Lab • At the time of her arrival Wilkins is away on other matters • When Wilkins returns, he discovers that his lab is taken over by Franklin • He notices that Franklin is very intelligent and is able to work independently • She spends hundreds of hours perfecting her X-ray Diffraction images and • hand written calculations • Wilkins is still under the impression that Franklin is his assistant • There is a lot of tension in the lab due to miscommunication and personality • clashes

19. Franklin’s Work

20. TWO FORMS OF DNA In 1951 Rosalind Franklin discovers the Two Forms of DNA through her X-ray diffraction images. A – Dry Form B – Wet Form Photo 51

21. X-Ray Crystallography

22. Watson and Crick’s Work

23. Watson and Crick’s Work In 1951 James Watson traveled from the United States to work with Francis Crick at Cambridge University Watson and Crick used the “Model Building” approach They physically built models out of wire, sheet metal, nuts and bolts to come up with the structure of DNA Why did they build models? “Sometimes the fingers can grasp what the mind cannot” (Biology the Science of Life)

24. Watson & Crick’s early model of DNA showed that the structure: • Was a Triple Helix • Had the Bases on the Outside • Had the Sugar Phosphate Backbone on the Inside However, Franklin disproves their model. This sends them back to the drawing board. Watson and Crick’s supervisor stops them from model building.

25. Social and Cultural Environment • Science at the time was a male dominated field • Women did not receive equal treatment • Women were forbidden in the lunch room • Franklin is unhappy at King’s College • She has no one to share ideas and collaborate with • She is fed up and decides to leave King’s College • But before she does, Franklin promises to finish writing up her research papers • In the process of her move, Wilkins gets hold of Franklin’s work which contained the famous photo 51

26. In 1951, Maurice Wilkins gives James Watson Rosalind Franklin’s work

27. Watson: “The instant I saw the picture my mouth fell open and my pulse began to race.” Page 196: Rosalind Franklin The Dark Lady of DNA

28. How Watson and Crick Solved the DNA Structure They already knew from Franklin and Wilkins’ work that DNA was in the form of a Double Helix Photo 51 They used Chargaff’s Rule to figure out how the 4 Bases match up in pairs

29. How Watson and Crick Solved the DNA Structure • They discovered that: • The Phosphate Backbone was on the outside • Which protected the Bases on the inside • DNA acts as a Template or a Copying Mechanism for reproduction

30. “Nature” Watson & Crick quickly published their Scientific Journal called “Nature” on April 25th 1953

31. The Nobel Prize • In 1962 Watson, Crick & Wilkins won the Nobel Prize for their • discovery of the structure of DNA • However, there is no mention of Franklin’s key work.

32. Discovering the Structure of DNA enabled the Scientific Community to understand the “Secret of Life” and how all life on earth is passed down from generation to generation

33. DNA Applications Science and Technology have advanced astronomically since the discovery in 1953 Here are some of the achievements since that time: • Cloning • Genetically Modified Foods • Genetic Engineering • DNA Fingerprinting/Analysis