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Ch. 16 DNA

Ch. 16 DNA. DNA: the Central Dogma, history, structure Replication. History: timeline, people and their accomplishments. Mendel (heredity) Sutton Chromosomes Thomas Hunt Morgan (flies, linkage) Griffith (1928) transformation and mice Avery and colleagues (1944):

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Ch. 16 DNA

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  1. Ch. 16DNA 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. 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 ReplicationEnzymesLeading and Lagging strands Okazaki FragmentsAnti-parallel Video

  9. “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. 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 primersEventual 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.

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