1. “The Blueprint of Life”
Chapter 12: DNA
“The Blueprint of Life”

2. Chapter 12.1 (Pg. 338-343): Identifying the Substance of Genes

3. What makes up a gene?
Scientists wanted to understand chemical nature of the gene
Frederick Griffith
Wanted to know how bacteria cause pneumonia in mice
Isolated two similar types (strains) of bacteria
S Strain: causes pneumonia
R Strain: harmless

4. Griffith’s Experiments
Injected mice with different bacteria
S Strain: Mouse Died
R Strain: Mouse Lives
S Strain (Heated): Mouse Lives
S Strain (Heated) and R Strain: Mouse Dies
What Happened?

5. Transformation
The harmless bacteria changed into the disease causing bacteria
Some ‘chemical factor’ transferred from the heat-killed S Strain cells into the living R Strain cells
The ability to cause disease was inherited by the R Strain

6. What is the Chemical Factor?
1944: Oswald Avery
Mixed heat-killed S strain and R Strain bacteria with different enzymes

7. Hershey-Chase Experiment
1952: Alfred Hershey and Martha Chase
Used bacterial viruses to identify genetic material
Bacteriophage: virus that infects bacteria by injecting its genetic information
Contain DNA core and protein coat

8. Hershey-Chase Experiment
Used radioactive phosphorous and sulfur
Acted as markers
All radioactivity in bacteria was phosphorous
Concluded that genetic material of bacteriophage was DNA

9. The Role of DNA Store Information Copy Information
Transmit Information