DNA

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The lecture for DNA (CH 9 TC Section 10.1 CP) for CCHS biology

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DNA

  1. 1. DNA
  2. 2. Identifying the Hereditary Material <ul><li>Protein first thought to be the genetic material </li></ul><ul><li>Several experiments to determine what it actually was. </li></ul><ul><ul><li>Griffith (1928) </li></ul></ul><ul><ul><li>Avery (1944) </li></ul></ul><ul><ul><li>Hershey and Chase (1952) </li></ul></ul>
  3. 3. Griffith -
  4. 4. Griffith <ul><li>Proved that there was a material that could be passed between generations and individuals </li></ul><ul><li>Proved that the capsule was not passable </li></ul><ul><li>Question: </li></ul><ul><ul><li>If DNA denatures (falls apart) at 90 º C and most proteins at 60 º C what factors might have changed the out come of his experiment? </li></ul></ul>
  5. 5. Avery <ul><li>Designed a series of experiments using hydrolytic enzymes to break up certain organic molecules but not others </li></ul>Dead mouse Dead mouse Dead mouse Living mouse DNAase DNA Lipase Lipids Protease Proteins Amylase Carbs Result Enzyme Organic Molecules
  6. 6. Hershey and Chase <ul><li>Labeled proteins and DNA with radioactive isotopes </li></ul><ul><li>Allowed infection of bacteria </li></ul><ul><li>Spun solution </li></ul><ul><ul><li>DNA in pellet therefore in bacteria </li></ul></ul><ul><ul><li>Protein in supernatant therefore do not enter cell </li></ul></ul>
  7. 7. Structure of DNA <ul><li>Made of Nucleotides </li></ul><ul><ul><li>Phosphate </li></ul></ul><ul><ul><li>Deoxyribose </li></ul></ul><ul><ul><li>Nitrogenous Base </li></ul></ul><ul><li>Four basic nitrogen containing bases </li></ul><ul><ul><li>Adenine </li></ul></ul><ul><ul><li>Guanine </li></ul></ul><ul><ul><li>Cytosine </li></ul></ul><ul><ul><li>Thymine </li></ul></ul>
  8. 8. Bases <ul><li>Purines </li></ul><ul><ul><li>Adenine and Guanine </li></ul></ul><ul><ul><li>Double ringed chemical structures </li></ul></ul><ul><li>Pyrimidines </li></ul><ul><ul><li>Thymine and Cytosine </li></ul></ul><ul><ul><li>Single ringed chemical structures </li></ul></ul>
  9. 9. Bases <ul><li>Purines </li></ul><ul><ul><li>Adenine and Guanine </li></ul></ul><ul><ul><li>Double ringed chemical structures </li></ul></ul><ul><li>Pyrimidines </li></ul><ul><ul><li>Thymine and Cytosine </li></ul></ul><ul><ul><li>Single ringed chemical structures </li></ul></ul>
  10. 10. Base Pairing Rules <ul><li>Question </li></ul><ul><ul><li>If DNA molecules do not bulge or indent what might the base pairing rules be considering the width and shape of the bases? </li></ul></ul>
  11. 11. Base Pairing Rules <ul><li>Adenine and Thymine Pair </li></ul><ul><li>Guanine and Cytosine Pair </li></ul>
  12. 12. Base Pairing <ul><li>Hydrogen bonds form between nitrogenous bases </li></ul><ul><ul><li>Three bonds between G and C </li></ul></ul><ul><ul><li>Two bonds between A and T </li></ul></ul><ul><li>Strands run antiparallel to each other </li></ul>
  13. 13. Double Helix
  14. 14. Double Helix History <ul><li>1953- Watson and Crick determine the structure of the macro-molecule DNA </li></ul><ul><ul><li>Using Chargaff’s rule, Rosalind Franklin’s X-ray crystallography picture of DNA </li></ul></ul><ul><li>DNA makes a full twist every ten base pairs </li></ul><ul><li>DNA remains the same width through out the length </li></ul>
  15. 15. Replication of DNA <ul><li>How does DNA replicate? </li></ul>
  16. 16. Replication of DNA <ul><li>How does DNA replicate? </li></ul>
  17. 17. Replication of DNA <ul><li>How does DNA replicate? </li></ul>
  18. 19. Replication <ul><li>Requires Several Enzymes </li></ul><ul><ul><li>Helicase- Unwinds original DNA </li></ul></ul><ul><ul><li>Polymerase-Builds new DNA </li></ul></ul><ul><li>Area of Replication is called a Replication Fork </li></ul>
  19. 20. DNA Repair <ul><li>DNA replication enzymes sometimes make mistakes. </li></ul><ul><li>Mistake = Mutation </li></ul><ul><li>New DNA strands are “proofread” for mistakes. </li></ul><ul><li>Results in greatly reduced mistakes </li></ul>

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