1. Drill
“All living things have me in them. Some people call me the ‘code of life.’ I was discovered in The amount of me in a person’s body could stretch 13.5 times to the Sun. In a chimpanzee, I am 98.5% similar to that of a human. Who am I?”

2. DNA: The Genetic Material
Section 12.1
Discovery of the Genetic Material
April 6, 2009

3. The Miraculous Acid
In 1874, Friedrich Miescher discovered acid molecules in the nuclei of pus cells.
This acid became known as deoxyribonucleic acid or DNA.

4. What is the genetic material?
Frederick Griffith – British microbiologist
In 1928, first to show that bacteria are capable of transferring genetic information.
This became known as the “transforming principle.”

5. Griffith’s Experiment
Used two strains of Pneumococcus bacteria:
S – strain
has mucus coating.
will cause fatal pneumonia in mice.
R – strain
has no coating.
does not harm mice.
S strain
R- strain

6. Griffith’s Experiment

7. Griffith’s Conclusion
What? You want me to just tell you…
Griffith did not know that the “transforming principle” was DNA.
Today we know that bacterial cells have small circular molecules of DNA called plasmids that can be passed between bacteria.

8. Oswald Avery Canadian physician and bacteriologist
In 1944, with coworkers, McCarty & MacLeod, he discovered that the “transforming principle” was DNA.
Very cautious to report his findings.

9. Avery, McCarty, & MacLeod, 1944
Repeated Griffith’s experiments with R- and S-strain Pneumococcus bacteria.
Purified extracts of S-strain bacteria.
Treated extracts with protease – an enzyme that destroys proteins
Bacteria still transform.
Treated extracts with deoxyribonuclease – an enzyme that eliminates DNA
No transformation.

10. Alfred Hershey & Martha Chase
American geneticists
In 1952, identified DNA to be the genetic material of phages – small viruses that infect bacteria -- and ultimately, all organisms.

11. The Blender Experiment

12. Section 12.1 Big Ideas
It took almost 80 years between the discovery of DNA and scientist’s understanding of its significance.
Significant scientific discovery results from the application of the scientific method.

13. Section 12.1 Big Ideas
Science is often advanced by the careful repetition, with modification, of the experiments of others.
DNA is the genetic material of all living organisms.

14. References: www.blc.arizona.edu/ INTERACTIVE/DNA3/DNA1.html
Publicschedule.html