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Ch. 9 Notes DNA: The Genetic Material By: Brianna Shields December 8, 2005.

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Presentation on theme: "Ch. 9 Notes DNA: The Genetic Material By: Brianna Shields December 8, 2005."— Presentation transcript:

1 Ch. 9 Notes DNA: The Genetic Material By: Brianna Shields December 8, 2005

2 DO NOW 1. Which scientist(s) “discovered” transformation? 2. Hershey and Chase verified the finding that what material is transferred during transformation? 3. What type of lab organism did Hershey and Chase use in their experiments?

3 List the terms in your vocab notebook, leaving about 3-4 spaces between each term Vaccine Virulent Transformation Bacteriophage Double Helix Nucleotide Deoxyribose Base-pairing Rules Complementary Base Pair DNA Replication DNA Helicase Replication Fork DNA Polymerase

4 GOALS Relate Griffith’s conclusions to the observations he made during the transformation experiments Summarize the steps involved in Avery’s transformation experimentsand state the results Evaluate the results of the Hershey and Chase experiment Describe the three components of a nucleotide Develop a model of the structure of a DNA molecule Evaluate the contributions of Chargaff, Franklin and Wilkins in helping Watson and Crick determine the double helical structure of DNA Relate the role of the base pairing rules to the structure of DNA Summarize the process of DNA replication Describe how errors are connected during DNA replication Compare the number of replication forks in prokaryotic and eukaryotic DNA

5 DNA: The Genetic Material Griffith’s Experime nt Trying to develop a vaccine (killed/weakened bacteria or virus introduced to body to protect from future infection)

6 DNA: The Genetic Material Griffith’s Experime nt Two strains of streptococcus pneumoniae S - virulent (disease causing), has capsule, grows in smooth colonies R- non disease causing, no capsule, grows in rough colonies

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8 DNA: The Genetic Material Griffith’s Experime nt 1. Mice injected with S died 2. Mice injected with R were healthy

9 DNA: The Genetic Material Griffith’s Experime nt 3. Was bacterial capsule causing death in mice?

10 DNA: The Genetic Material Griffith’s Experime nt 4. Inject mice with dead S bacteria- mice remained healthy

11 DNA: The Genetic Material Griffith’s Experime nt 5. Injected mice with heat killed S bacteria- (can’t reproduce but still have capsule)- mice lived

12 DNA: The Genetic Material Griffith’s Experime nt 6. Injected mixed harmless live R with heat killed S into mice- mice died

13 DNA: The Genetic Material Griffith’s Experime nt 7. Mouse blood contained R bacteria that had acquired capsules (somehow changed and became virulent S bacteria) Discovered TRANSFORMATION

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16 DNA: The Genetic Material Transformati on Change in genotype caused when cells take in foreign genetic material

17 DNA: The Genetic Material Avery’s Experiment What substance is responsible for transformation? Added protein destroying enzymes to heat killed S and healthy R mixture- transformation occurred Added DNA destroying enzymes to same mixture- transformation stopped

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19 DNA: The Genetic Material Hershey and Chase Experiment Wanted to confirm that DNA (not proteins) carried genetic material

20 DNA: The Genetic Material Hershey and Chase Experiment Known facts A. Viruses made of DNA or RNA surrounded by protective protein coat

21 DNA: The Genetic Material Hershey and Chase Experiment Known facts B. Bacteriophages (viruses) infecxt bacteria to produce more viruses (released when bacteria host ruptures)

22 DNA: The Genetic Material Hershey and Chase Experiment Known facts C. Only DNA in phage contained phosphorus D. Only protein coat in phage contained sulfur

23 DNA: The Genetic Material Hershey and Chase Experiment 1. Grew a sample of T2 bacteriophage in radioactive sulfur medium (would be used in T2’s protein coat)

24 DNA: The Genetic Material Hershey and Chase Experiment 2. Grew a sample of T2 bacteriophage in radioactive phosphorus medium (would be used in T2’s DNA)

25 DNA: The Genetic Material Hershey and Chase Experiment 3. Allowed S and P labeled phages to infect E. coli bacteria Can detect radioactive S and P to see if DNA, protein or both are transferred to E. coli

26 DNA: The Genetic Material Hershey and Chase Experiment 4. S and P phages removed from bacteria using blender 5. Centifuge spins heavy bacteria to bottom and light phages to liquidy top of mixture

27 DNA: The Genetic Material Hershey and Chase Experiment 6. Findings: A. S label found only in phages (protein never injected into E. coli) B. P label found mostly in bacteria (DNA transferred to E. coli) C. New generation of phages from bursted bacteria also contained radioactive DNA

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30 DNA: The Genetic Material Hershey and Chase Experiment 7. Conclusion: DNA is transferred from virus to bacteria Protein remains outside cell DNA must be hereditary material (atleast in viruses)

31 Assessment One Summarize Griffith’s transformation experiments Describe how Avery’s experiment supplied evidence that DNA, not protein is the genetic material Describe the contributions of Hershey and Chase to the understanding that DNA is the genetic material Why did heat kill Griffith’s S bacteria? What might Hershey and Chase have concluded if they had found P and S in the bacteria cells?

32 DNA: The Genetic Material Watson and Crick Established the structure of DNA Made a tin and wire model of DNA

33 DNA: The Genetic Material Structure of DNA 1. Double helix- 2 strands of linked nucleotides twisted around like a winding staircase

34 DNA: The Genetic Material Structure of DNA 2. Nucleotides- subunits that make up DNA, composed of: Phosphate group Five carbon sugar molecule (deoxyribose) Nitrogen containing base (four kinds) Adenine Guanine Thymine Cytosine Bases pair up to create” ladder rungs”

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37 DNA: The Genetic Material Structure of DNA 3. Base classification Purines- double ring of C and N atoms Adenine and Guanine Pyrimidines- single ring of C and N atoms Thymine and Cytosine

38 DNA: The Genetic Material Structure of DNA 4. Helix held together by weak hydrogen bonds between paired bases

39 DNA: The Genetic Material Chargaff Discovered base pairing rule Amounts of adenine and thymine in DNA are always the same Amounts of cytosine and guanine in DNA are always the same Amounts of A and T, and G and C differ

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41 DNA: The Genetic Material Wilkins and Franklins Photograp hs Bounced X rays off DNA to create pattern scattered onto film Photos indicate DNA is a tightly coiled helix with 2 chains of nucleotides

42 DNA: The Genetic Material Pairing between bases Because of size and structure of bases, only certain ones pair up to hold DNA together Adenine - Thymine Guanine - Cytosine

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45 DNA: The Genetic Material Pairing between bases Results in complementary base pairs Sequence on one strand of DNA can determine sequence of other strand

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47 Assessment Two Describe the three parts of a DNA molecule Relate the base pairing rules to the structure of the DNA Describe the two pieces of information from other scientists that enabled Watsons and Crick to discover the double helical structure of DNA Explain why the two strands of the double helix are described as complementary What would be the complementary strand to DNA with the following base sequence: AGCTTAGTCA

48 DNA: The Genetic Material Replication of DNA Making a copy of DNA Complementary strands of DNA serve as template for replicating DNA Occurs during S phase of cell cycle (before division)

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50 DNA: The Genetic Material Replication of DNA Steps: A. DNA helicase unwinds and opens DNA by breaking H bonds between bases

51 DNA: The Genetic Material Replication of DNA Steps: B. Helix separates at replication forks (Y shape), proteins attach to DNA and hold helix open

52 DNA: The Genetic Material Replication of DNA Steps: C. DNA polymerase enters fork, moves along DNA strand adding nucleotides to exposed bases according to pairing rule Proofreads, removes and fixes any mismatched nucleotides Reduces error to 1 in a billion

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54 DNA: The Genetic Material Replication of DNA Steps: D. DNA polymerase continues until DNA is copied, then it is signaled to detach

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56 DNA: The Genetic Material Replication of DNA Result: 2 new DNA double helices created (identical to each other and original DNA)

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58 DNA: The Genetic Material Rate of DNA replication In circular prokaryotic DNA 2 replication forks that move away from one another until they meet on other side of DNA circle

59 DNA: The Genetic Material Rate of DNA replication In eukaryotic DNA End o end replication would take a month for one strand of DNA Have multiple replication forks so several DNA portions are replicated simultaneously One human chromosome takes 8 hours

60 Assessment Three Explain the two roles that enzymes play in DNA replication Explain the relationship between DNA polymerases and mutation State the effect of multiple replication forks on the speed of replication in eukaryotes If a mutation occurs during the formation of an egg cell or sperm cell, is that mutation more significant or less significant than a mutation that occurs in a body cell?

61 Websites Gene Scene DNA Workshop The Geee! In Genome Putting DNA to work Kids Genetics: DNA Hershey and Chase Experiment Animation DNA Replication Animation Another DNA Replication Animation


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