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DNA and Replication copyright cmassengale
History of DNA copyright cmassengale
History of DNA <ul><li>Early scientists thought  protein  was the cell’s hereditary material because it was  more complex ...
Transformation <ul><li>Fred Griffith  worked with  virulent S  and  nonvirulent R  strain  Pneumoccocus  bacteria </li></u...
 
Griffith Experiment copyright cmassengale
History of DNA <ul><li>Chromosomes  are made of both DNA and protein </li></ul><ul><li>Experiments on  bacteriophage  viru...
Discovery of DNA Structure <ul><li>Erwin Chargaff  showed the amounts of the four bases on DNA ( A,T,C,G) </li></ul><ul><l...
Chargaff’s Rule <ul><li>Adenine   must pair with  Thymine </li></ul><ul><li>Guanine  must pair with  Cytosine </li></ul><u...
DNA Structure <ul><li>Rosalind Franklin  took diffraction  x-ray  photographs of DNA crystals </li></ul><ul><li>In the 195...
Rosalind Franklin copyright cmassengale
DNA Structure copyright cmassengale
DNA <ul><li>Two strands coiled called a  double helix </li></ul><ul><li>Sides  made of a pentose sugar  Deoxyribose  bonde...
DNA Double Helix copyright cmassengale Nitrogenous Base (A,T,G or C) “ Rungs of ladder” “ Legs of ladder” Phosphate & Suga...
DNA <ul><li>Stands for  Deoxyribonucleic acid </li></ul><ul><li>Made up of subunits called  nucleotides   </li></ul><ul><l...
DNA Nucleotide O copyright cmassengale O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 ...
Pentose Sugar <ul><li>Carbons are numbered clockwise 1’ to 5’ </li></ul>copyright cmassengale C H2 O C 1 C 4 C 3 C 2 5 Sug...
DNA copyright cmassengale P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A
Antiparallel Strands <ul><li>One strand of DNA goes from 5’ to 3’ (sugars) </li></ul><ul><li>The other strand is  opposite...
Nitrogenous Bases <ul><li>Double ring  PURINES </li></ul><ul><li>Adenine (A) </li></ul><ul><li>Guanine (G) </li></ul><ul><...
Base-Pairings <ul><li>Purines  only pair   with  Pyrimidines </li></ul><ul><li>Three  hydrogen bonds required to bond  Gua...
<ul><li>Two  hydrogen bonds are required to bond Adenine & Thymine </li></ul>copyright cmassengale T A
Complementary  base pairing G G A T T A A C T G C A T C
DNA Gene Trait Protein
Copyright Cmassengale
<ul><li>Chromosomes may differ in the position of the  Centromere , the place on the chromosome where spindle fibers are a...
 
<ul><li>The major histone proteins: </li></ul><ul><li>Histone  Mol. Wt No. of  Percentage </li></ul><ul><li>  Amino acid L...
<ul><li>The basic structural unit of chromatin, the  nucleosome , was described by  Roger Kornberg  in  1974.  </li></ul><...
Question: <ul><li>If there is  30%  Adenine , how much  Cytosine  is present? </li></ul>copyright cmassengale
Answer: <ul><li>There would be 20%  Cytosine </li></ul><ul><li>Adenine (30%) = Thymine (30%) </li></ul><ul><li>Guanine (20...
DNA Replication copyright cmassengale
Replication Facts <ul><li>DNA has to be copied  before a cell divides </li></ul><ul><li>DNA is copied during the  S  or sy...
Synthesis Phase (S phase) <ul><li>S phase during  interphase  of the cell cycle </li></ul><ul><li>Nucleus of eukaryotes </...
DNA Replication <ul><li>Begins at   Origins of Replication </li></ul><ul><li>Two strands open forming  Replication Forks (...
DNA Replication <ul><li>Enzyme  Helicase  unwinds and separates the 2 DNA strands by breaking the  weak hydrogen bonds </l...
DNA Replication <ul><li>Enzyme  Topoisomerase  attaches to the 2 forks of the bubble to  relieve stress  on the  DNA molec...
DNA Replication <ul><li>Before  new DNA strands can form, there must be  RNA primers  present to start the addition of new...
copyright cmassengale
DNA Replication <ul><li>DNA polymerase  can only add nucleotides to the  3’ end  of the DNA  </li></ul><ul><li>This causes...
Remember HOW the Carbons Are Numbered! copyright cmassengale O O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) ...
Remember the Strands are Antiparallel copyright cmassengale P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G ...
Synthesis of the New DNA Strands <ul><li>The  Leading Strand  is synthesized as a  single strand  from the  point of origi...
Synthesis of the New DNA Strands <ul><li>The  Lagging Strand  is  synthesized  discontinuously   against  overall directio...
Lagging Strand Segments <ul><li>Okazaki Fragments  -   series of short segments on the  lagging strand </li></ul><ul><li>M...
Joining of Okazaki Fragments <ul><li>The enzyme  Ligase  joins the Okazaki fragments together to make one strand </li></ul...
Replication of Strands Replication Fork Point of Origin copyright cmassengale
Semiconservative Model of Replication <ul><li>Idea presented by  Watson & Crick </li></ul><ul><li>The  two strands of the ...
DNA Damage & Repair <ul><li>Chemicals & ultraviolet radiation  damage the DNA in our body cells </li></ul><ul><li>Cells mu...
 
Question: <ul><li>What would be the complementary DNA strand for the following DNA sequence? </li></ul><ul><li>DNA 5’-CGTA...
Answer: <ul><li>DNA  5’-CGTATG-3’ </li></ul><ul><li>DNA  3’-GCATAC-5’ </li></ul>copyright cmassengale
<ul><li>C to G and G to C </li></ul><ul><li>DNA simplicity </li></ul><ul><li>That’s the double helix code that makes you, ...
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Biology lecture 4

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Biology lecture 4

  1. 1. DNA and Replication copyright cmassengale
  2. 2. History of DNA copyright cmassengale
  3. 3. History of DNA <ul><li>Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA </li></ul><ul><li>Proteins were composed of 20 different amino acids in long polypeptide chains </li></ul>copyright cmassengale
  4. 4. Transformation <ul><li>Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria </li></ul><ul><li>He found that R strain could become virulent when it took in DNA from heat-killed S strain </li></ul><ul><li>Study suggested that DNA was probably the genetic material </li></ul>copyright cmassengale
  5. 6. Griffith Experiment copyright cmassengale
  6. 7. History of DNA <ul><li>Chromosomes are made of both DNA and protein </li></ul><ul><li>Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material </li></ul>Radioactive 32 P was injected into bacteria! copyright cmassengale
  7. 8. Discovery of DNA Structure <ul><li>Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G) </li></ul><ul><li>In a body or somatic cell: </li></ul><ul><li>A = 30.3% </li></ul><ul><li>T = 30.3% </li></ul><ul><li>G = 19.5% </li></ul><ul><li>C = 19.9% </li></ul>copyright cmassengale
  8. 9. Chargaff’s Rule <ul><li>Adenine must pair with Thymine </li></ul><ul><li>Guanine must pair with Cytosine </li></ul><ul><li>The bases form weak hydrogen bonds </li></ul>copyright cmassengale G C T A
  9. 10. DNA Structure <ul><li>Rosalind Franklin took diffraction x-ray photographs of DNA crystals </li></ul><ul><li>In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays </li></ul>copyright cmassengale
  10. 11. Rosalind Franklin copyright cmassengale
  11. 12. DNA Structure copyright cmassengale
  12. 13. DNA <ul><li>Two strands coiled called a double helix </li></ul><ul><li>Sides made of a pentose sugar Deoxyribose bonded to phosphate (PO 4 ) groups by phosphodiester bonds </li></ul><ul><li>Center made of nitrogen bases bonded together by weak hydrogen bonds </li></ul>copyright cmassengale
  13. 14. DNA Double Helix copyright cmassengale Nitrogenous Base (A,T,G or C) “ Rungs of ladder” “ Legs of ladder” Phosphate & Sugar Backbone
  14. 15. DNA <ul><li>Stands for Deoxyribonucleic acid </li></ul><ul><li>Made up of subunits called nucleotides </li></ul><ul><li>Nucleotide made of: </li></ul><ul><li>1. Phosphate group </li></ul><ul><li>2. 5-carbon sugar </li></ul><ul><li>3. Nitrogenous base </li></ul>copyright cmassengale
  15. 16. DNA Nucleotide O copyright cmassengale O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)
  16. 17. Pentose Sugar <ul><li>Carbons are numbered clockwise 1’ to 5’ </li></ul>copyright cmassengale C H2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)
  17. 18. DNA copyright cmassengale P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A
  18. 19. Antiparallel Strands <ul><li>One strand of DNA goes from 5’ to 3’ (sugars) </li></ul><ul><li>The other strand is opposite in direction going 3’ to 5’ (sugars) </li></ul>copyright cmassengale
  19. 20. Nitrogenous Bases <ul><li>Double ring PURINES </li></ul><ul><li>Adenine (A) </li></ul><ul><li>Guanine (G) </li></ul><ul><li>Single ring PYRIMIDINES </li></ul><ul><li>Thymine (T) </li></ul><ul><li>Cytosine (C) </li></ul>copyright cmassengale T or C A or G
  20. 21. Base-Pairings <ul><li>Purines only pair with Pyrimidines </li></ul><ul><li>Three hydrogen bonds required to bond Guanine & Cytosine </li></ul>copyright cmassengale C G 3 H-bonds
  21. 22. <ul><li>Two hydrogen bonds are required to bond Adenine & Thymine </li></ul>copyright cmassengale T A
  22. 23. Complementary base pairing G G A T T A A C T G C A T C
  23. 24. DNA Gene Trait Protein
  24. 25. Copyright Cmassengale
  25. 26. <ul><li>Chromosomes may differ in the position of the Centromere , the place on the chromosome where spindle fibers are attached during cell division. </li></ul><ul><li>In general, if the centromere is near the middle, the chromosome is metacentric </li></ul><ul><li>If the centromere is toward one end, the chromosome is acrocentric or submetacentric </li></ul><ul><li>If the centromere is very near the end, the chromosome is telocentric . </li></ul>
  26. 28. <ul><li>The major histone proteins: </li></ul><ul><li>Histone Mol. Wt No. of Percentage </li></ul><ul><li> Amino acid Lys + Arg </li></ul><ul><li>H1 22,500 244 30.8 </li></ul><ul><li>H2A 13,960 129 20.2 </li></ul><ul><li>H2B 13,774 125 22.4 </li></ul><ul><li>H3 15,273 135 22.9 </li></ul><ul><li>H4 11,236 102 24.5 </li></ul>The DNA double helix is bound to proteins called histones .  The histones have  positively charged (basic) amino acids to bind the negatively charged (acidic) DNA.  Here is an SDS gel of histone proteins, separated by size
  27. 29. <ul><li>The basic structural unit of chromatin, the nucleosome , was described by Roger Kornberg in 1974. </li></ul><ul><li>Two types of experiments led to Kornberg’s proposal of the nucleosome model. </li></ul><ul><li>First, partial digestion of chromatin with micrococcal nuclease (an enzyme that degrades DNA) was found to yield DNA fragments approximately 200 base pairs long . </li></ul><ul><li>In contrast, a similar digestion of naked DNA (not associated with protein) yielded a continuous smear randomly sized fragments . </li></ul><ul><li>These results suggest that the binding of proteins to DNA in chromatin protects the regions of DNA from </li></ul><ul><li>nuclease digestion, so that enzyme can </li></ul><ul><li>attack DNA only at sites separated by </li></ul><ul><li>approximately 200 base pairs. </li></ul>
  28. 30. Question: <ul><li>If there is 30% Adenine , how much Cytosine is present? </li></ul>copyright cmassengale
  29. 31. Answer: <ul><li>There would be 20% Cytosine </li></ul><ul><li>Adenine (30%) = Thymine (30%) </li></ul><ul><li>Guanine (20%) = Cytosine (20%) </li></ul><ul><li>Therefore, 60% A-T and 40% C-G </li></ul>copyright cmassengale
  30. 32. DNA Replication copyright cmassengale
  31. 33. Replication Facts <ul><li>DNA has to be copied before a cell divides </li></ul><ul><li>DNA is copied during the S or synthesis phase of interphase </li></ul><ul><li>New cells will need identical DNA strands </li></ul>copyright cmassengale
  32. 34. Synthesis Phase (S phase) <ul><li>S phase during interphase of the cell cycle </li></ul><ul><li>Nucleus of eukaryotes </li></ul>copyright cmassengale Mitosis -prophase -metaphase -anaphase -telophase G 1 G 2 S phase interphase DNA replication takes place in the S phase.
  33. 35. DNA Replication <ul><li>Begins at Origins of Replication </li></ul><ul><li>Two strands open forming Replication Forks (Y-shaped region) </li></ul><ul><li>New strands grow at the forks </li></ul>copyright cmassengale Replication Fork Parental DNA Molecule 3’ 5’ 3’ 5’
  34. 36. DNA Replication <ul><li>Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds </li></ul><ul><li>Single-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted </li></ul>copyright cmassengale
  35. 37. DNA Replication <ul><li>Enzyme Topoisomerase attaches to the 2 forks of the bubble to relieve stress on the DNA molecule as it separates </li></ul>copyright cmassengale Enzyme DNA Enzyme
  36. 38. DNA Replication <ul><li>Before new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides </li></ul><ul><li>Primase is the enzyme that synthesizes the RNA Primer </li></ul><ul><li>DNA polymerase can then add the new nucleotides </li></ul>copyright cmassengale
  37. 39. copyright cmassengale
  38. 40. DNA Replication <ul><li>DNA polymerase can only add nucleotides to the 3’ end of the DNA </li></ul><ul><li>This causes the NEW strand to be built in a 5’ to 3’ direction </li></ul>Direction of Replication copyright cmassengale RNA Primer DNA Polymerase Nucleotide 5’ 5’ 3’
  39. 41. Remember HOW the Carbons Are Numbered! copyright cmassengale O O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)
  40. 42. Remember the Strands are Antiparallel copyright cmassengale P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A
  41. 43. Synthesis of the New DNA Strands <ul><li>The Leading Strand is synthesized as a single strand from the point of origin toward the opening replication fork </li></ul>copyright cmassengale RNA Primer DNA Polymerase Nucleotides 3’ 5’ 5’
  42. 44. Synthesis of the New DNA Strands <ul><li>The Lagging Strand is synthesized discontinuously against overall direction of replication </li></ul><ul><li>This strand is made in MANY short segments It is replicated from the replication fork toward the origin </li></ul>copyright cmassengale RNA Primer Leading Strand DNA Polymerase 5’ 5’ 3’ 3’ Lagging Strand 5’ 5’ 3’ 3’
  43. 45. Lagging Strand Segments <ul><li>Okazaki Fragments - series of short segments on the lagging strand </li></ul><ul><li>Must be joined together by an enzyme </li></ul>copyright cmassengale Lagging Strand RNA Primer DNA Polymerase 3’ 3’ 5’ 5’ Okazaki Fragment
  44. 46. Joining of Okazaki Fragments <ul><li>The enzyme Ligase joins the Okazaki fragments together to make one strand </li></ul>copyright cmassengale Lagging Strand Okazaki Fragment 2 DNA ligase Okazaki Fragment 1 5’ 5’ 3’ 3’
  45. 47. Replication of Strands Replication Fork Point of Origin copyright cmassengale
  46. 48. Semiconservative Model of Replication <ul><li>Idea presented by Watson & Crick </li></ul><ul><li>The two strands of the parental molecule separate, and each acts as a template for a new complementary strand </li></ul><ul><li>New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA </li></ul>copyright cmassengale Parental DNA DNA Template New DNA
  47. 49. DNA Damage & Repair <ul><li>Chemicals & ultraviolet radiation damage the DNA in our body cells </li></ul><ul><li>Cells must continuously repair DAMAGED DNA </li></ul><ul><li>Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA </li></ul><ul><li>DNA polymerase and DNA ligase replace and bond the new nucleotides together </li></ul>copyright cmassengale
  48. 51. Question: <ul><li>What would be the complementary DNA strand for the following DNA sequence? </li></ul><ul><li>DNA 5’-CGTATG-3’ </li></ul>copyright cmassengale
  49. 52. Answer: <ul><li>DNA 5’-CGTATG-3’ </li></ul><ul><li>DNA 3’-GCATAC-5’ </li></ul>copyright cmassengale
  50. 53. <ul><li>C to G and G to C </li></ul><ul><li>DNA simplicity </li></ul><ul><li>That’s the double helix code that makes you, you and makes me, me. </li></ul>

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