1. DNA replication
Chapter 16

3. Summary of history Griffith Mice & Strep Transformation
External DNA taken in by cell

4. Summary of history Hershey-Chase Bacteriophages
Supported heredity information was DNA

5. Bacteriophages

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7. Summary of history Franklin X-ray diffraction Double helix
Watson-Crick
Double helix model

8. Nucleic acid structure
DNA deoxyribonucleic acid
RNA ribonucleic acid
Nucleotides

9. Nucleotide structure 1. 5 carbon sugar (ribose) 2. Phosphate
3. Nitrogenous base

10. Nucleotide structure

11. Nitrogenous base Purines (2 rings) Adenine(A) & Guanine(G)
Pyrimidines (1 ring)
Cytosine (C), Thymine (T) DNA only
Uracil (U) RNA only

13. Phosphodiester bond Links 2 sugars (nucleotides)

15. Nucleic acids 5’ Phosphate group (5’C) at one end
3’ Hydroxyl group (3’C) at the other end
Sequence of bases is expressed in the 5’ to 3’ direction
GTCCAT 5’pGpTpCpCpApT---OH 3’

16. Double helix Complementary Sequence on one chain of DNA
Determines sequence of other chain
5’-ATTGCAT-3’
3’-TAACGTA-5’

18. Double Helix Complementary
Two-ringed purine pairs with a one-ringed pyrimidine
Diameter of base pairs are the same
Adenine (A) forms two hydrogen bonds with Thymine (T)
Guanine (G) forms three hydrogen bonds with cytosine (C)

20. Fig. 16-7 5 end Hydrogen bond 3 end 1 nm 3.4 nm 3 end 0.34 nm
(a) Key features of DNA structure
(b) Partial chemical structure

22. Double Helix Composed of 2 complementary phosphodiester strands
Strands are antiparrellel
Sugar-phosphates are the backbone
Bases extend into interior of helix
Base-pairs form to join the two strands

23. Duplication DNA unzips New strand forms based on existing strand
Old strand is saved
Compliment of the new strand
New DNA-one old strand & one new strand
Semiconservative replication

26. Fig. 16-9-3 A T A T A T A T C G C G C G C G T A T A T A T A A T A T A
(a) Parent molecule
(b) Separation of strands
(c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand

27. Duplication study Meselson and Stahl Bacteria 14N and 15N
Semiconservative method.

28. Fig. 16-10 (a) Conservative model (b) Semiconserva- tive model
First replication
Second replication
Parent cell
(a) Conservative model
(b) Semiconserva- tive model
(c) Dispersive model

29. Summary
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30. Duplication E coli (bacteria) OriC Origins of replication
Starting point in DNA synthesis
Replication is bidirectional
Proceeds in both directions from origin
5’to 3’direction

31. Duplication Bacteria Circular DNA One origin Eurkaryotes
Multiple origins

33. Duplication Replication bubble: Separation of strands of DNA
Replication of DNA
Replication fork:
Y-shaped region
End of replication bubble
Parental DNA unwinding

34. Duplication
Replication fork:
Site of active replication

36. Duplication

37. Duplication Enzymes DNA helicase:
Enzyme opens helix starts duplication
Separates parental strands
Single-strand binding protein:
Binds to unpaired DNA
After separation
Stabilizes DNA

38. Duplication Enzymes Primer: Section of RNA
Complementary to the parental DNA
Synthesis occurs only one direction
5’ to 3’
DNA primase:
Enzyme creates the primer

39. Duplication Enzymes DNA polymerases: Help lengthen new strand of DNA
Adds new nucleotides strand
Synthesis occurs only one direction
5’ to 3’
Adding new nucleotides to the 3’OH

40. Duplication Enzymes Topoisomerase: Relieves strain of unwinding DNA
DNA pol1:
Removes primers
Replaces with DNA nucleotides
DNA ligase:
Creates phosphodiester bonds between Okazaki fragments

42. Duplication Leading strand:
DNA continuous 5’ to 3’ replication (towards fork)
Template is 3’ to 5’
Lagging strand:
DNA duplicated in short segments (away from fork)
Okazaki fragments:
Short stretches of new DNA-lagging side

43. Duplication
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44. Duplication
Unzips (helicase, single-strand binding protein, topoisomerase)
Primer
DNA polymerase (5’to3’)
DNA ligase

46. Duplication

48. Nucleoside triphosphate
Fig
New strand 5 end
Template strand 3 end
5 end
3 end
Sugar A T A T
Base
Phosphate C G C G G C G C
DNA polymerase
3 end A T A T
3 end C
Pyrophosphate C
Nucleoside triphosphate
5 end
5 end

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50. Fig. 16-13 Primase Single-strand binding proteins 3 Topoisomerase 5
RNA primer 5 5 3
Helicase

51. Fig. 16-15b Origin of replication 3 5 RNA primer 5 “Sliding clamp”
DNA pol III
Parental DNA 3 5 5 3 5

52. Overall directions of replication
Fig a
Overview
Origin of replication
Leading strand
Lagging strand
Lagging strand 2 1
Leading strand
Overall directions of replication

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54. Single-strand binding protein Overall directions of replication
Fig
Overview
Origin of replication
Leading strand
Lagging strand
Leading strand
Lagging strand
Single-strand binding protein
Overall directions of replication
Helicase
Leading strand 5
DNA pol III 3 3
Primer
Primase 5
Parental DNA 3
DNA pol III
Lagging strand 5
DNA pol I
DNA ligase 4 3 5 3 2 1 3 5

55. Overall directions of replication
Fig
Overview
Origin of replication
Leading strand
Lagging strand
Lagging strand 2 1
Leading strand
Overall directions of replication 3 5 3
Template strand 5 3
RNA primer 3 5 1 5
Okazaki fragment 3 5 3 1 5 5 3 3 2 1 5 5 3 3 5 2 1 5 3 3 1 5 2
Overall direction of replication

57. Duplication

58. Duplication

59. Duplication Telomers: Sequences at ends of chromosomes
Short nucleotide sequences
Repeated times
Prevents 5’ end erosion
Telomerase:
Enzyme that lengthens telomers
Usually in germ cells

61. Repairs Mismatched pair: Duplication error Enzymes remove error
Nucleotide excision repair:
Damaged section removed
Nuclease
New nucleotides fill gap
Complement DNA section not damaged

62. Chromosome packaging Chromatin: Complex composed of DNA and proteins
40% DNA 60% protein
Heterochromatin:
More compacted chromatin
Euchromatin:
Loosely packed chromatin

63. Chromosome packaging Double helix Histones: proteins
Nucleosome: DNA coiled around 8 histones (10nm)
Nucleosomes then coil (30nm)
Looped domains attach to chromosome scaffold (300nm)
Domains coil form chromosome

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