2. Part 1 Discovery of DNA & its structure

3. Learning Target 2. Know the contributions of ……make a timeline……
Griffin
Avery-MacLeod-McCarty
Hershey-Chase.
Watson and Crick
Franklin
Chargaff
……make a timeline……

4. Griffith & Bacterial Transformation
1928- Frederick Griffith
Studied 2 strains of pneumonia from mice
1 caused pneumonia
1 did not cause pneumonia
Non-pneumonia kind was “transformed” into pneumonia kind

5. Avery-MacLeod-McCarty
1944—Oswald Avery
They used process of elimination to determine which molecule gets transferred
DNA was the molecule being transferred from 1 bacteria to another in Griffith’s experiment

6. Hershey & Chase 1952—Alfred Hershey & Martha Chase
Studied bacteriophages
Bacteria killing viruses
Attached radioactive markers to proteins and to DNA to see which one was genetic material
Determined that DNA, not protein functions as genetic material

7. Phage
head
Tail
Tail fiber
DNA
Bacterial
cell
100 nm

8. Other clues to DNA’s Structure: Chargaff
Erwin Chargaff (American biochemist) 1950
“Chargaff’s Rules”
Species have different amounts of A, T, G & C
Analyzed amounts of Adenine, cytosine, guanine & thymine
Amount of A = T
Amount of C = G

9. Wilkins & Franklin Maybe a “twisted” structure Maybe a helix
Early 1950’s– Maurice Wilkins & Rosalind Franklin
From images captured through X-ray crystallographers
Maybe a “twisted” structure
Maybe a helix
Maybe 2 strands
Maybe nitrogen bases in middle

10. Rosalind Franklin and her X-ray diffraction photo of DNA
(a) Rosalind Franklin
Franklin’s X-ray diffraction
Photograph of DNA
(b)

11. Watson & Crick James Watson (American biologist)
Francis Crick (British physicist)
1953  put all the clues together
Built wire/tin model
“Double Helix”
Nobel Prize 1962
Watson, Crick, Wilkins