1. Chapter 8 How Genes Work
8.1
Understanding DNA

2. Gregor Mendel Mendel studied how traits were inherited
“Father of Modern Genetics”

3. ..however even with all Mendel discovered, scientists didn’t know
What material actually carried genetic information
How genetic information was carried
What genes were

4. Frederick Griffith 1928 London Bacteriologist
Working with 2 strains of Pneumococcus
Made an interesting discovery

5. The following cartoons are taken from:
The Cartoon Guide to Genetics by Larry Gonick and Mark Wheelis

11. Virulent
causing disease

12. A process in which a bacterium takes up foreign DNA
Transformation
A process in which a bacterium takes up foreign DNA

13. Oswald Avery Early 1940’s New York Biologist
Wanted to identify Griffith’s transforming substance
Was it DNA or protein?

14. Avery’s experiments

15. Avery concluded that DNA was the genetic material responsible for transformation.

16. Alfred Hershey & Martha Chase
1952
Scientists working at Cold Springs Harbor Laboratory
Used viruses to confirm that DNA was hereditary material

17. T2 Bacteriophage

18. Actual T2 Photomicrograph

19. How phages infect bacteria

20. The Famous “Blender Experiment”
** Sulfur is found in protein

21. Blender Experiment Part 2
** Phosphorus is found in DNA

22. Hershey & Chase
Concluded that DNA is hereditary material

23. Scientists knew DNA was composed of nucleotides

24. Erwin Chargaff 1949 Biochemist Columbia University, NY
Found a correlation between the relative amounts of the bases

25. Chargaff noted that….
Adenine
Thymine
Cytosine
Guanine

26. This suggested a pattern or regularity on the structure of DNA
Chargaff’s Rules
In DNA….
A = T
G = C
This suggested a pattern or regularity on the structure of DNA

27. Rosalind Franklin used x-ray diffraction to provide evidence of the helical structure of DNA

28. Watson & Crick 1952 Cavendish Laboratories
Deduced the structure of DNA using information form Chargaff, Franklin & others
Built famous model

29. One of the keys was figuring out how the base pairs fit together

31. Then how the chains fit together

32. How the chains coiled to form a double helix

33. And finally… how the entire molecule appeared

34. Take a closer look….

35. The process of copying DNA
DNA Replication
The process of copying DNA

36. Replication begins with complementary strands of DNA

40. Let’s Review

41. DNA Replication – another look

42. Change in the genotype of an individual
Mutation
Change in the genotype of an individual

43. Mutations can be caused by
Addition of a base into DNA
Deletion of a base from DNA
Damage to a base already in DNA

44. Environmental agent that can alter the structure of DNA
Mutagen
Environmental agent that can alter the structure of DNA

45. DNA damage from UV light is a great example
PLEASE WEAR YOUR SUNSCREEN !