1. DNA: the Central Dogma, history, structure Replication
Ch. 16 DNA
DNA: the Central Dogma, history, structure
Replication

2. History: timeline, people and their accomplishments
Mendel (heredity)
Sutton Chromosomes
Thomas Hunt Morgan (flies, linkage)
Griffith (1928) transformation and mice
Avery and colleagues (1944):
proposed DNA as the transforming agent
Chargaff (late 40’s-early 50’s)
base pairing (AT CG)
Hershey-Chase (1952) DNA IS hereditary material
Watson and Crick (1953) (Franklin) chemical structure of DNA
Meselson-Stahl mid 1950’s
DNA Replication details

3. Griffith:
Transformation

4. Hershey / Chase (the hereditary material is not a protein)
Radio-active P and S

5. Purine? Pyrimidine? You have 6 billion pair in every cell!
Whose rule? A-T C-G
Purine? Pyrimidine? You have 6 billion pair in every cell!

6. Chargaff’s Rule
Purines (A, G, double rings) always pair with Pyrimidines (T, C, single rings)
A-T, C-G (& in RNA? ____)
Old AP test question: if in a cell the DNA bases are 17% A’s then what are the %’s of the other bases?
CUT your PY or Pure Silver (Ag)

7. DNA Replication: SEMICONSERVATIVE MODEL
How did they (Meselson-Stahl) prove this? FIG 16.8

8. KNOW: Steps of Replication Enzymes Leading and Lagging strands Okazaki Fragments Anti-parallel
Video

9. This process is fueled by… nucleoside triphosphates
“Bubbles”
Replication forks,
simultaneous replication
**Eukaryotes - multiple
origins of replication
**Prokaryotes have one
Semi-conservative
This process is fueled by… nucleoside triphosphates

10. DNA is made from 5’ to 3’ and it is read from 3’-5’.
The 3’ end is the end which elongates (grows)
Why is this direction important to consider in Replication?

11. What do the terms 5’ and 3’ mean?

12. Okazaki fragments (are of the lagging strand)
Leading & Lagging strands, made 5’-3’
Okazaki fragments (are of the lagging strand)
ENZYMES: helicase, DNA Polymerase, ligase

13. Enzymes :
Helicase
•Single strand binding proteins •Primase (RNA Primer) •DNA Polymerase •Ligase
•Nuclease and DNA Polymerase (both are repair enzymes)

14. Let’s see this in Action
Leading Strand (Nobelprize.org)
Lagging Strand (Nobelprize.org)
Overall (wiley)
Overall 3D view (wehi.edu.au or dnai.org) (Youtube has a music version)

15. Telomeres Unfilled gap left at the ends of the DNA strands due to the use of RNA primers Eventual shortening of DNA over time

16. Enzyme: Telomerase extends the (3’) long strand so the 5’ strand can finish.
Telomerase is found in germ cells that give rise to gametes.

17. How’s it all fit? DNA coiling – Let’s see it!
DNA from a single skin cell, if straightened out, would be about six feet long but invisible. Half a gram of DNA, uncoiled, would stretch to the sun. Again, you couldn't see it.