Ch.16 dna - notes version

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Ch.16 dna - notes version

  1. 1. The structure of a DNA stand
  2. 2. The double helix
  3. 3. Evidence that DNA is genetic material• Griffith – bacterial transformation• Avery – discovered that the transforming agent is DNA• Hershey & Chase – used bacteriophages and radioactive isotopes to demonstrate that DNA, not protein is genetic material• Chargraff – found that A = T and C = G
  4. 4. Bacterial Transformation•Study by Griffith•Assimilation of external DNA by a cell•Inherited by future generations
  5. 5. The Hershey-Chase experiment: phages
  6. 6. The Hershey-Chase experiment
  7. 7. A model for DNA replication: the basic concept
  8. 8. Three alternative models of DNA replication
  9. 9. The Meselson-Stahl experiment tested three models of DNA replication
  10. 10. Origins of replication in eukaryotes
  11. 11. Antiparallel StrandsDNA is elongated in the5’ to 3’ direction
  12. 12. DNA is elongated in the5’ to 3’ directionLeading strandLagging strandOther strand –elongated in piecesOkazaki fragments
  13. 13. Priming DNA for Replication
  14. 14. Summary of DNA Replication5’ to 3’ directionRNA primerLeading/ lagging strandsEnzymes
  15. 15. DNA Damage & RepairThymine Dimer –covalent bond betweenthymines distorts DNANuclease cuts outdamaged DNADNA Polymerase fixeserrorDNA Ligase seals DNA
  16. 16. Telomeres & TelomerasesEnds of linear DNA getshorter and shorterIn comes Telomerase-Lengthens the end of ashortened DNA strand-Uses RNA templateTelomeres-non-coding DNA at endof chromosomes-repeated sequence-gives DNA room to beshortened
  17. 17. Figure 16.19b Telomeres and telomerase

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