1. DNA: The Building Block of Life
…the basis for inheritance and evolutionary theory!

2. Where do we find DNA? All living things contain DNA
DNA is the basis of heredity (inheritance)
Encodes the “blueprints” that direct all functions within cells and organisms

3. The Search for Genetic Material: 1. Griffith (1928)
Worked with two kinds of bacteria; found bacteria could incorporate external genetic material in a process now called transformation

4. The Search for Genetic Material: 2. Avery (1944)
Continued the work of Griffith & proposed that DNA was the molecule that transformed the bacteria

5. The Search for Genetic Material: 3. Hershey & Chase (1952)
Proved that viruses contain DNA that can be injected into bacterial cells AND can replicate within those cells!
Radioactive phosphorus “labeled” the DNA

6. The Search for Genetic Material: 4. Chargaff (1947)
Reported ratio of nitrogenous bases was species specific
Determined # of adenines = # thymines and # of guanines = # cytosines… this is known as Chargaff’s Rule!
A - T C - G
Complementary base pairs

7. The Guys who put it all together… 5.Watson & Crick
Determined 3D shape of DNA
Idea of the “double helix” based on 1 purine pairing with 1 pyrimidine (nitrogenous bases) and a sugar-phosphate backbone

9. The unsung hero of this story…
Rosalind Franklin: X-ray crystallographer- her images are what Watson & Crick used in their work

10. Semi-Conservative Model
Each side of DNA helix complementary to the other
When replicating, 2 daughter DNA strands have 1 old strand from parent DNA and 1 new strand