1. Structure & Replication
DNA
Structure & Replication

2. Organic compounds Can you name all 4 macromolecules and their monomer?
Carbohydrate
Monosaccharide
Lipid
Fatty acid/glycerol
Protein
Amino Acid
Nucleic Acid
Nucleotide

3. Contributing Scientists
Hershey & Chase
Chargaff
Franklin
Watson and Crick

4. Hershey & Chase What is genetic material made of? DNA vs. Protein
What is genetic material made of?
DNA vs. Protein

5. Chargaff Take a look at Chargaff’s data on pg. 107 of your textbook.
What patterns do you notice?

6. Franklin Maurice Wilkins and Rosalind Franklin Rosalind Franklin
Were using a technique called X-ray diffraction to study molecular structure
Rosalind Franklin
Produced a picture of the DNA molecule using this technique
The cross in the center indicates that the molecule is helical in shape.
The angle of the cross showed the pitch of the helix.
The distance between bars showed the turns of the helix to be 3.4nm apart.
The distance between the middle of the pattern and the top showed the repeating structure every 0.34nm.
(a) Rosalind Franklin
Franklin’s X-ray diffraction
Photograph of DNA
(b)
Figure 16.6 a, b

7. Watson & Crick
Repeatedly built models based on incoming evidence about the structure of DNA.
The first failed model did not take into account Franklins nor Chargaff’s findings.
Once DNA structure was elucidated, it led to all sorts of discoveries about how DNA is copied, used, and inherited.

8. Watson & Crick
Ted Talk

9. Nucleotide Components
Phosphate Group
Sugar
Nitrogenous Base H

10. Sugar

11. Bases
Adenine
Thymine
Guanine
Cytosine

12. Sugar Phosphate Backbone

13. DNA – Double Stranded, Antiparallel
Hydrogen Bonds
Covalent Bond

14. DNA forms a double helix

15. Supercoiling of DNA Nucleosomes help to supercoil the DNA.

16. Nucleosomes
Textbook pg. 348: do the activity “Visualizing Nucleosomes” Use this link (on Haiku): and click on the two “Discussed structures” at the bottom of the page to manipulate the 3D structures

17. Supercoiling Animation: http://www.youtube.com/watch?v=OjPcT1uUZiE

18. DNA Replication
The structure of DNA suggests a method for copying DNA.
When does DNA replication occur?
During the S-phase of interphase!
DNA replication is semi-conservative.
Meselson and Stahl obtained evidence for this.

19. 1. 3. 2. 4.

20. Meselson & Stahl
Read about their experiment on pg. 112 – 113, then do the DBQ starting on pg. 113 – 114.

21. Helicase
Unwinds & unzips

23. DNA Gyrase AKA – topoisomerase
Releases the strain that develops ahead of the helicase.
DNA Gyrase

24. Single Strand Binding Proteins
Keep the strands apart long enough to be copied.
SSBP

25. http://www. biologyexams4u

26. DNA Primase
Creates an RNA primer (5’ to 3’)

27. After Primase

28. DNA Polymerase III
Adds free-floating DNA nucleotides (5’ to 3’ covalent bonds)
Complementary base pairing

29. After DNA polymerase III

30. Okazaki fragments

32. DNA Polymerase I
Removes RNA primer & replaces it with DNA

33. Ligase
Seals the gaps between fragments

34. As ligase acts

35. After ligase

37. The end REsult