2. 1 DNA and Replication

3. 2 History of DNA

4. 3 DNA DNA.DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell.

5. 4 DNA Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops.

6. 5 Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA.

7. 6 History of DNA Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins were composed of 20 different amino acids in long polypeptide chains

8. 7 Transformation Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria He found that R strain could become virulent when it took in DNA from heat-killed S strain Study suggested that DNA was probably the genetic material

9. 8 Griffith Experiment

10. 9 History of DNA Chromosomes are made of both DNA and protein Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material Radioactive 32 P was injected into bacteria!

11. 10 Discovery of DNA Structure Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G) In a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9%

12. 11 Chargaff’s Rule Adenine ThymineAdenine must pair with Thymine Guanine CytosineGuanine must pair with Cytosine The bases form weak hydrogen bonds G C TA

13. 12 DNA Structure Rosalind Franklin took diffraction x-ray photographs of DNA crystals In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays

14. 13 Watson and Crick

15. 14 Rosalind Franklin

16. 15 Pairs What have we learned about DNA so far? What different experiments led to our current understanding of DNA? What is Chargaff’s Rule?

17. 16 DNA Structure

18. 17 DNA Two strands coiled called a double helix Sides made of a pentose sugar Deoxyribose bonded to phosphate (PO 4 ) groups by phosphodiester bonds Center made of nitrogen bases bonded together by weak hydrogen bonds

19. 18 DNA Double Helix Nitrogenous Base (A,T,G or C) “Rungs of ladder” “Legs of ladder” Phosphate & Sugar Backbone

20. 19 Helix Most DNA has a right-hand twist with 10 base pairs in a complete turnMost DNA has a right-hand twist with 10 base pairs in a complete turn Left twisted DNA is called Z-DNA or southpaw DNALeft twisted DNA is called Z-DNA or southpaw DNA Hot spots occur where right and left twisted DNA meet producing mutationsHot spots occur where right and left twisted DNA meet producing mutations

21. 20 DNA Stands for Deoxyribonucleic acid nucleotidesMade up of subunits called nucleotides Nucleotide made of:Nucleotide made of: Phosphate group 1.Phosphate group 5-carbon sugar 2.5-carbon sugar Nitrogenous base 3.Nitrogenous base

22. 21 DNA Nucleotide O O=P-O OPhosphate Group Group N Nitrogenous base (A, G, C, or T) (A, G, C, or T) CH2 O C1C1 C4C4 C3C3 C2C2 5 Sugar Sugar(deoxyribose)

23. 22 Pentose Sugar Sugars are numbered clockwise 1’ to 5’ CH2 O C1C1 C4C4 C3C3 C2C2 5 Sugar Sugar(deoxyribose)

24. 23 DNA 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 TA

25. 24 Pairs What three structures make up a nucleotide? What are the four nitrogenous bases? What is the base pairing rule?

26. 25 Antiparallel Strands One strand of DNA goes from 5’ to 3’ (sugars) The other strand is opposite in direction going 3’ to 5’ (sugars)

27. 26 Nitrogenous Bases Double ring PURINESDouble ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINESSingle ring PYRIMIDINES Thymine (T) Cytosine (C) T or C A or G

28. 27 Base-Pairings Purines only pair with Pyrimidines Three hydrogen bonds required to bond Guanine & Cytosine CG 3 H-bonds

29. 28 T A Two hydrogen bonds are required to bond Adenine & Thymine

30. 29 Question: Adenine CytosineIf there is 30% Adenine, how much Cytosine is present?

31. 30 Answer: CytosineThere would be 20% Cytosine Adenine (30%) = Thymine (30%)Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%)Guanine (20%) = Cytosine (20%) Therefore, 60% A-T and 40% C-GTherefore, 60% A-T and 40% C-G

32. 31 RNA

33. 32 RNA Differs from DNA 1.RNA has a sugar ribose DNA has a sugar deoxyribose 2.RNA contains the base uracil (U) DNA has thymine (T) 3.RNA molecule is single-stranded DNA is double-stranded

34. 33 Structure of RNA

35. 34. Three Types of RNA Messenger RNA (mRNA) carries genetic information to the ribosomesMessenger RNA (mRNA) carries genetic information to the ribosomes Ribosomal RNA (rRNA), along with protein, makes up the ribosomesRibosomal RNA (rRNA), along with protein, makes up the ribosomes Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesizedTransfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized

36. 35 DNA by the Numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun.

37. 36 DNA Model Make your own DNA model A short research paper will accompany your model. Include the the structures discussed in your notes: Double helix, nucleotides, phosphate groups, sugars, and bases

38. 37 DNA Song We love DNA made of nucleotides sugar, phosphate, and a base bonded down one side. Adenine and thymine make a lovely pair cytosine without guanine would feel very bare. D, D, DNA different sets of genes look inside the nucleus for instructions to make proteins. We love DNA it’s the code of life and the genetic makeup of all you have in side.

39. 38 DNA Song Assignment Requirements: Due by the next time we meet Explain what makes up a DNA strand: nucleotide sugar phosphate bases (nitrogenous) Explain the base pairing concept: thymine pairing with adenine cytosine paring with guanine Explain where DNA is found and that they are the instructions used to make proteins. Explain that it is the genetic make-up of all organisms. Explain how DNA is different than RNA

40. 39 DNA Replication

41. 40 Replication Facts DNA has to be copied before a cell dividesDNA has to be copied before a cell divides DNA is copied during the S or synthesis phase of interphaseDNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strandsNew cells will need identical DNA strands

42. 41 Synthesis Phase (S phase) S phase during interphase of the cell cycle Nucleus of eukaryotes Mitosis -prophase -metaphase -anaphase -telophase G1G1 G2G2 S phase interphase DNA replication takes place in the S phase.

43. 42 DNA Replication Begins at Origins of ReplicationBegins at Origins of Replication Two strands open forming Replication Forks (Y-shaped region)Two strands open forming Replication Forks (Y-shaped region) New strands grow at the forksNew strands grow at the forks ReplicationFork Parental DNA Molecule 3’ 5’ 3’ 5’

44. 43 DNA Replication As the 2 DNA strands open at the origin, Replication Bubbles formAs the 2 DNA strands open at the origin, Replication Bubbles form Eukaryotic chromosomes have MANY bubbles Prokaryotes (bacteria) have a single bubble Bubbles

45. 44 Pairs What is the replication fork? When is DNA copied? How is eukaryotic replication different than prokaryotic replication?

46. 45 DNA Replication Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bondsEnzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds Single-Strand Binding ProteinsSingle-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted

47. 46 DNA Replication Enzyme Topoisomerase relieve stressDNA moleculeEnzyme Topoisomerase attaches to the 2 forks of the bubble to relieve stress on the DNA molecule as it separates Enzyme DNA Enzyme

48. 47 DNA Replication Before RNA primersBefore new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides PrimasePrimase is the enzyme that synthesizes the RNA Primer DNA polymerase can then add the new nucleotides

49. 48

50. 49 DNA Replication DNA polymerase can only add nucleotides to the 3’ end of the DNADNA polymerase can only add nucleotides to the 3’ end of the DNA This causes the NEW strand to be built in a 5’ to 3’ directionThis causes the NEW strand to be built in a 5’ to 3’ direction RNAPrimer DNA Polymerase Nucleotide 5’ 3’ Direction of Replication

51. 50 Remember HOW the Carbons Are Numbered! O O=P-O OPhosphate Group Group N Nitrogenous base (A, G, C, or T) (A, G, C, or T) CH2 O C1C1 C4C4 C3C3 C2C2 5 Sugar Sugar(deoxyribose)

52. 51 Remember the Strands are Antiparallel 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 TA

53. 52 Synthesis of the New DNA Strands The Leading Strand single strandThe Leading Strand is synthesized as a single strand from the point of origin toward the opening replication fork RNAPrimer DNA Polymerase Nucleotides 3’5’

54. 53 Synthesis of the New DNA Strands The Lagging Strand is discontinuouslyThe Lagging Strand is synthesized discontinuously against overall direction of replication This strand is made in MANY short segments It is replicated from the replication fork toward the origin RNA Primer Leading Strand DNA Polymerase 5’5’ 5’ 3’ Lagging Strand 5’ 3’

55. 54 Lagging Strand Segments Okazaki Fragments - lagging strandOkazaki Fragments - series of short segments on the lagging strand Must be joined together by an enzymeMust be joined together by an enzyme Lagging Strand RNAPrimerDNAPolymerase 3’ 5’ Okazaki Fragment

56. 55 Joining of Okazaki Fragments The enzyme Ligase joins the Okazaki fragments together to make one strandThe enzyme Ligase joins the Okazaki fragments together to make one strand Lagging Strand Okazaki Fragment 2 DNA ligase DNA ligase Okazaki Fragment 1 5’ 3’

57. 56 Replication of Strands Replication Fork Point of Origin

58. 57 Pairs In what direction do nucleotides have to be added to the existing strand? How is the leading strand different than the lagging strand? List and describe the function of the enzymes involved with replication.

59. 58 Proofreading New DNA DNA polymerase initially makes about 1 in 10,000 base pairing errorsDNA polymerase initially makes about 1 in 10,000 base pairing errors Enzymes proofread and correct these mistakesEnzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errorsThe new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors

60. 59 Semiconservative Model of Replication Idea presented by Watson & CrickIdea presented by Watson & Crick TheThe two strands of the parental molecule separate, and each acts as a template for a new complementary strand New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA Parental DNA DNA Template New DNA

61. 60 DNA Damage & Repair Chemicals & ultraviolet radiation damage the DNA in our body cells Cells must continuously repair DAMAGED DNA Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA DNA polymerase and DNA ligase replace and bond the new nucleotides together

62. 61 Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’

63. 62 Answer: DNA 5’-GCGTATG-3’ DNA 3’-CGCATAC-5’

64. 63 Replication Animation http://highered.mcgraw- hill.com/sites/0072437316/student_view0/chapter14 /animations.html#