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 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

20. 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)

22. 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