1. DNA History, Structure, & Function
AP Biology

2. History of DNA
AP Biology ch. 16.1

3. DNA History: Miescher
1869, Friedrich Miescher discovers nuclein by extracting white blood cells from pus-laden bandages

4. DNA History: Frederick Griffith
1928: tried to find a pneumonia vaccine
Found “transforming principle” instead

6. DNA History: Avery & McCarty
1944: Followed up on Griffith’s experiment
Demonstrated that DNA was Griffith’s “transforming principle”

8. DNA History: Hershey & Chase
1952: Used phages to demonstrate that DNA was genetic material
Radiolabeled phages with 35S and 32P to distinguish protein from nucleic acid

10. DNA History: Erwin Chargaff
1950: determined that adenine molecules always pair with Thymine molecules and cytosine molecules always pair with guanine molecules

11. DNA History: Franklin & Wilkins
1953: Used X-ray diffraction
Had the evidence that the double helix existed but didn’t put it all together

12. DNA History: Watson & Crick
1953: Saw Franklin’s X-rays, and built the first, correct, 3D model of DNA

13. Summary of DNA History
Many scientists expanded upon previous scientific ideas to correctly show:
Structure of DNA (double helix of nucleotides)
Function of DNA (genetic material of life)

14. Overview: DNA Structure
Chromosomes:
DNA wound up around histone proteins
Onion (8 pairs) Human (23 pairs)

15. Overview: DNA Structure
Long molecule made up of repeating units called nucleotides

16. Overview: DNA Structure
Nucleotide:
5-Carbon Sugar (Deoxyribose)
Phosphate Group (PO4)
Nitrogen Base:
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

17. Overview: DNA Structure
Important Chemistry of DNA:
Nitrogen base groups:
Purines (2 ring)
Adenine
Guanine
Pyrimidines (1 ring)
Cytosine
Thymine

18. Overview: DNA Structure
Important Chemistry of DNA:
Sugar carbon atoms are numbered (1-5)
Phosphodiester bonds hold backbone together
Hydrogen bonds hold nitrogen bases together

19. DNA Replication
AP Biology ch 16.2

20. Remember You started as: Now you are: one cell with one set of DNA
trillions of cells large
Each cell contains the one set of DNA

21. How does each cell get DNA?
DNA Replication
Process by which DNA is copied
Occurs in all living organisms
Many enzymes are used!

22. DNA Structure

23. Step 1: DNA Replication Start with one complete strand of DNA
Template Strand
Parent Strand

24. Step 2: DNA Replication
Topoisomerase
unwinds DNA

25. Step 3: DNA Replication
Helicase
Unzips template strand
At H bonds

26. Step 4: DNA Replication
Replication fork forms

27. Step 5: DNA Replication DNA polymerase Finds starter sequence
Adds free DNA nucleotides
Checks the sequence
Makes repairs

28. Step 6: Okazaki Fragments
DNA is antiparallel
One strand of DNA:
synthesized continuously
The other strand of DNA:
is synthesized in segments
(O.F.)

29. Step 7: DNA Replication
DNA Ligase
Connects O.F.

30. Step 8: DNA Replication Two identical strands of DNA are formed
Each strand has a parent and daughter strand

31. The Others

32. Replication Animations
PBS:
St. Olaf:

33. Gene Expression

34. DNA Function (Gene Expression)