1. DNA: The Genetic Material
Chapter 14

2. What is the genetic material?
Protein vs DNA
Griffith, Avery, Macleod and McCarty, Hershey and Chase

3. Griffith: Transformation

4. Avery, MacLeod, an McCarty
Repeated Griffiths except removed almost all Protein from the viri
5 findings
1. The elemental composition agreed closely with that of DNA
2. When spun at high speeds in ultracentrifuge it migrated to the same level as DNA
3. Extracting lipids and proteins did not reduce transforming activity
4. Protein- digesting enzymes did not affect transforming activity, nor did RNA digesting enzymes
5. DNA-Digesting enzymes destroyed all transforming activity

5. Hershey and Chase

6. DNA Structure Miescher Components known but structure and mystery
1. A FIVE-carbon sugar
2. A phosphate group
3. A nitrogen containing base ( purine vs Pyrimidine)

7. Phosphodiester Bonds Make backbone of DNA
Formed by Dehydration Synthesis

8. Chargoff, Franklin, and Wilkins
Chargoff’s rules
A=T, and G=C
There are always an equal number of Purines and Pyrimidines
Franklin and Wilkins worked with x-ray diffraction

9. Watson and Crick Took everyone else’s information and built a model
1. Phosphodiester backbone
2. Complementarity of bases
3. Antiparallel configuration

11. Meselson and Stahl Looking at DNA replication 3 possibilities
Conservative
Semiconservative
Dispersive

13. Overview of Replication
Initiation
Elongation
Termination

14. Prokaryotic Replication

15. DNA replication Enzymes
Polymerase 1-acts on lagging strand to remove primers
Polymerase 2- involved in DNA repair
Polymerase 3- main replication polymerase
Helicase- Unwinds DNA
Gyrase- lowers torsional strain
Primase- synthesizes RNA primers
Ligase- joins the ends of DNA segments
SSB- stabilizes single stranded regions

16. Imporant Facts about DNA replication
Occurs in the 5’ to 3’ direction
Leading strand and Lagging strand (Okazaki fragments)
Occurs in a repication fork
Beta subunit holds pol III on
Replisome contains all necessary enzymes for replication

18. Videos http://highered.mcgraw-hill.com/olc/dl/120076/micro04.swf

19. Eukaryotic Replication
Complicated by the larger amount of DNA and Linear structure of the chromasomes
Multiple Origins
Same enzymes but they are more complex
Telomerase signals the end of replication

20. Why is Telomerase important?
When it doesn’t work the ends or Telomeres of DNA gradually shorten
This leads to aging
Linked to cancer

21. DNA Repair Mutagens constantly cause damage
DNA repair can restore damaged DNA
Specific
Photorepair using thymine dimer
Non specific
Excision Repair