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  • Figure 10.1 The chemical structure of a DNA polynucleotide.
  • Figure 10.1a The chemical structure of a DNA polynucleotide.
  • Figure 10.1b The chemical structure of a DNA polynucleotide.
  • Figure 10.3a Discoverers of the double helix.
  • Figure 10.3b Discoverers of the double helix.
  • Figure 10.4 A rope-ladder model of a double helix.
  • Figure 10.5 Three representatives of DNA.
  • Figure 10.7 Multiple "bubbles" in replicating DNA.
  • Figure 10.8 The flow of genetic information in a eukaryotic cell. (Step 1)
  • Figure 10.8 The flow of genetic information in a eukaryotic cell. (Step 2)
  • Figure 10.8 The flow of genetic information in a eukaryotic cell. (Step 3)
  • Figure 10.10 Transcription of DNA and translation of codons.
  • Figure 10.10 Transcription of DNA and translation of codons.
  • Figure 10.13b Transcription
  • Figure 10.14 The production of messenger RNA (mRNA) in a eukaryotic cell.
  • Figure 10.15 The structure of tRNA
  • Figure 10.16 The ribosome.
  • Figure 10.16a The ribosome.
  • Figure 10.16b The ribosome.
  • Figure 10.17 A molecule of mRNA.
  • Figure 10.18 The initiation of translation
  • Figure 10.19 The elongation of a polypeptide. (Step 1)
  • Figure 10.19 The elongation of a polypeptide. (Step 2)
  • Figure 10.19 The elongation of a polypeptide. (Step 3)
  • Figure 10.19 The elongation of a polypeptide. (Step 4)
  • Figure 10.20 A summary of transcription and translation. (Step 1)
  • Figure 10.20 A summary of transcription and translation. (Step 2)
  • Figure 10.20 A summary of transcription and translation. (Step 3)
  • Figure 10.20 A summary of transcription and translation. (Step 4)
  • Figure 10.20 A summary of transcription and translation. (Step 5)
  • Figure 10.20 A summary of transcription and translation. (Step 6)
  • Figure 10.21 The molecular basis of sickle-cell disease.
  • Figure 10.22a Base substitution of mutations and their effects.
  • Figure 10.22b Nucleotide deletion of mutations and their effects.
  • Figure 10.22c Nucleotide insertion of mutations and their effects.
  • Figure 10.24 Adenovirus
  • Figure 10.24 Adenovirus
  • Figure 10.25 Bacteriophages (viruses) infecting a bacterial cell.
  • Figure 10.26 Alternative phage reproductive cycles. (Step 1)
  • Figure 10.26 Alternative phage reproductive cycles. (Step 2)
  • Figure 10.26a Alternative phage reproductive cycles.
  • Figure 10.26b Alternative phage reproductive cycles.
  • Figure 10.26c Alternative phage reproductive cycles.
  • Figure 10.27 Tobacco mosaic virus
  • Figure 10.27b Tobacco mosaic virus
  • Figure 10.27a Tobacco mosaic virus
  • Figure 10.28 An influenza virus.
  • Figure 10.29 The reproductive cycle of an enveloped virus.
  • Figure 10.29a The reproductive cycle of an enveloped virus.
  • Figure 10.29b The reproductive cycle of an enveloped virus.
  • Figure 10.31 HIV, the AIDS virus.
  • Figure 10.32 The behavior of HIV nucleic acid in an infected cell.
  • Figure 10.32a The behavior of HIV nucleic acid in an infected cell.
  • Figure 10.32b HIV infecting a white blood cell.
  • Figure 10.33 AZT and the T nucleotide.
  • Figure 10.34 Mad cow disease.
  • Figure 10.35 Rounding up ducks in Vietnam to help prevent the spread of the Avian flu virus.
  • Figure 10.UN1 Transcription orientation diagram
  • Figure 10.UN2 Translation orientation diagram
  • Figure 10.UN3 Summary: DNA and RNA Structure
  • Figure 10.UN3a Summary: DNA and RNA Structure
  • Figure 10.UN3b Summary: DNA and RNA Structure
  • Figure 10.UN4 Summary: DNA Replication
  • Figure 10.UN5 Summary: DNA to Protein
  • Figure 10.UN6 Summary: Translation: The Players
  • Figure 10.UN7 Summary: Mutations
  • 10 lecture presentation0

    1. 1. © 2010 Pearson Education, Inc. DNA: STRUCTURE AND REPLICATION • DNA: – Was known to be a chemical in cells by the end of the nineteenth century – Has the capacity to store genetic information – Can be copied and passed from generation to generation
    2. 2. © 2010 Pearson Education, Inc. DNA and RNA Structure • DNA and RNA are nucleic acids. – They consist of chemical units called nucleotides. – The nucleotides are joined by a sugar-phosphate backbone. Animation: Hershey-Chase Experiment Animation: DNA and RNA Structure
    3. 3. Sugar-phosphate backbone Phosphate group Nitrogenous base DNA nucleotide Nucleotide Thymine (T) Sugar Polynucleotide DNA double helix Sugar (deoxyribose) Phosphate group Nitrogenous base (can be A, G, C, or T) Figure 10.1
    4. 4. Sugar-phosphate backbone Phosphate group Nitrogenous base DNA nucleotide Nucleotide Thymine (T) Sugar Polynucleotide Sugar (deoxyribose) Phosphate group Nitrogenous base (can be A, G, C, or T) Figure 10.1a
    5. 5. DNA nucleotide Thymine (T) Sugar (deoxyribose) Phosphate group Nitrogenous base (can be A, G, C, or T) Figure 10.1b
    6. 6. © 2010 Pearson Education, Inc. • The four nucleotides found in DNA differ in their nitrogenous bases. These bases are: – Thymine (T) – Cytosine (C) – Adenine (A) – Guanine (G) • RNA has uracil (U) in place of thymine.
    7. 7. © 2010 Pearson Education, Inc. Watson and Crick’s Discovery of the Double Helix • James Watson and Francis Crick determined that DNA is a double helix.
    8. 8. James Watson (left) and Francis Crick Figure 10.3a
    9. 9. © 2010 Pearson Education, Inc. • Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA. – Rosalind Franklin collected the X-ray crystallography data.
    10. 10. X-ray image of DNA Rosalind Franklin Figure 10.3b
    11. 11. © 2010 Pearson Education, Inc. • The model of DNA is like a rope ladder twisted into a spiral. – The ropes at the sides represent the sugar-phosphate backbones. – Each wooden rung represents a pair of bases connected by hydrogen bonds.
    12. 12. Twist Figure 10.4
    13. 13. © 2010 Pearson Education, Inc. • DNA bases pair in a complementary fashion: – Adenine (A) pairs with thymine (T) – Cytosine (C) pairs with guanine (G) Animation: DNA Double Helix Blast Animation: Hydrogen Bonds in DNA Blast Animation: Structure of DNA Double Helix
    14. 14. (c) Computer model (b) Atomic model(a) Ribbon model Hydrogen bond Figure 10.5
    15. 15. © 2010 Pearson Education, Inc. DNA Replication • When a cell reproduces, a complete copy of the DNA must pass from one generation to the next. • Watson and Crick’s model for DNA suggested that DNA replicates by a template mechanism. Animation: DNA Replication Review Animation: DNA Replication Overview
    16. 16. © 2010 Pearson Education, Inc. • DNA can be damaged by ultraviolet light. • DNA polymerases: – Are enzymes – Make the covalent bonds between the nucleotides of a new DNA strand – Are involved in repairing damaged DNA
    17. 17. © 2010 Pearson Education, Inc. • DNA replication in eukaryotes: – Begins at specific sites on a double helix – Proceeds in both directions Animation: Origins of Replication Animation: Leading Strand Animation: Lagging Strand
    18. 18. Origin of replication Origin of replication Origin of replication Parental strands Parental strand Daughter strand Two daughter DNA molecules Bubble Figure 10.7
    19. 19. THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN • DNA functions as the inherited directions for a cell or organism. • How are these directions carried out? © 2010 Pearson Education, Inc.
    20. 20. How an Organism’s Genotype Determines Its Phenotype • An organism’s genotype is its genetic makeup, the sequence of nucleotide bases in DNA. • The phenotype is the organism’s physical traits, which arise from the actions of a wide variety of proteins. © 2010 Pearson Education, Inc.
    21. 21. © 2010 Pearson Education, Inc. • DNA specifies the synthesis of proteins in two stages: – Transcription, the transfer of genetic information from DNA into an RNA molecule – Translation, the transfer of information from RNA into a protein
    22. 22. DNA Cytoplasm Nucleus Figure 10.8-1
    23. 23. RNA TRANSCRIPTION DNA Cytoplasm Nucleus Figure 10.8-2
    24. 24. TRANSLATION Protein RNA TRANSCRIPTION DNA Cytoplasm Nucleus Figure 10.8-3
    25. 25. © 2010 Pearson Education, Inc. From Nucleotides to Amino Acids: An Overview • Genetic information in DNA is: – Transcribed into RNA, then – Translated into polypeptides
    26. 26. © 2010 Pearson Education, Inc. • What are the rules for translating the RNA message into a polypeptide? • A codon is a triplet of bases, which codes for one amino acid.
    27. 27. © 2010 Pearson Education, Inc. The Genetic Code • The genetic code is: – The set of rules relating nucleotide sequence to amino acid sequence – Shared by all organisms
    28. 28. © 2010 Pearson Education, Inc. • Of the 64 triplets: – 61 code for amino acids – 3 are stop codons, indicating the end of a polypeptide
    29. 29. TRANSLATION Amino acid RNA TRANSCRIPTION DNA strand Polypeptide Codon Gene 1 Gene 3 Gene 2 DNA molecule Figure 10.10
    30. 30. TRANSLATION Amino acid RNA TRANSCRIPTION DNA strand Polypeptide Codon Figure 10.10
    31. 31. © 2010 Pearson Education, Inc. Transcription: From DNA to RNA • Transcription: – Makes RNA from a DNA template – Uses a process that resembles DNA replication – Substitutes uracil (U) for thymine (T) • RNA nucleotides are linked by RNA polymerase.
    32. 32. © 2010 Pearson Education, Inc. Initiation of Transcription • The “start transcribing” signal is a nucleotide sequence called a promoter. • The first phase of transcription is initiation, in which: – RNA polymerase attaches to the promoter – RNA synthesis begins
    33. 33. © 2010 Pearson Education, Inc. RNA Elongation • During the second phase of transcription, called elongation: – The RNA grows longer – The RNA strand peels away from the DNA template Blast Animation: Roles of RNA Blast Animation: Transcription
    34. 34. © 2010 Pearson Education, Inc. Termination of Transcription • During the third phase of transcription, called termination: – RNA polymerase reaches a sequence of DNA bases called a terminator – Polymerase detaches from the RNA – The DNA strands rejoin
    35. 35. © 2010 Pearson Education, Inc. The Processing of Eukaryotic RNA • After transcription: – Eukaryotic cells process RNA – Prokaryotic cells do not
    36. 36. © 2010 Pearson Education, Inc. • RNA processing includes: – Adding a cap and tail – Removing introns – Splicing exons together to form messenger RNA (mRNA) Animation: Transcription
    37. 37. (b) Transcription of a gene RNA polymerase Completed RNA Growing RNA Termination Elongation Initiation Terminator DNA Area shown in part (a) at left RNA Promoter DNA RNA polymerase DNA of gene Figure 10.13b
    38. 38. © 2010 Pearson Education, Inc. Translation: The Players • Translation is the conversion from the nucleic acid language to the protein language.
    39. 39. © 2010 Pearson Education, Inc. Messenger RNA (mRNA) • Translation requires: – mRNA – ATP – Enzymes – Ribosomes – Transfer RNA (tRNA)
    40. 40. Transcription Addition of cap and tail Coding sequence mRNA DNA Cytoplasm Nucleus Exons spliced together Introns removed Tail CapRNA transcript with cap and tail Exon Exon ExonIntronIntron Figure 10.14
    41. 41. © 2010 Pearson Education, Inc. Transfer RNA (tRNA) • Transfer RNA (tRNA): – Acts as a molecular interpreter – Carries amino acids – Matches amino acids with codons in mRNA using anticodons
    42. 42. tRNA polynucleotide (ribbon model) RNA polynucleotide chain Anticodon Hydrogen bond Amino acid attachment site tRNA (simplified representation) Figure 10.15
    43. 43. © 2010 Pearson Education, Inc. Ribosomes • Ribosomes are organelles that: – Coordinate the functions of mRNA and tRNA – Are made of two protein subunits – Contain ribosomal RNA (rRNA)
    44. 44. © 2010 Pearson Education, Inc. • A fully assembled ribosome holds tRNA and mRNA for use in translation.
    45. 45. Next amino acid to be added to polypeptide Growing polypeptide tRNA mRNA tRNA binding sites Codons Ribosome (b) The “players” of translation(a) A simplified diagram of a ribosome Large subunit Small subunit P site mRNA binding site A site Figure 10.16
    46. 46. tRNA binding sites Ribosome (a) A simplified diagram of a ribosome Large subunit Small subunit P site mRNA binding site A site Figure 10.16a
    47. 47. Next amino acid to be added to polypeptide Growing polypeptide tRNA mRNA Codons (b) The “players” of translation Figure 10.16b
    48. 48. © 2010 Pearson Education, Inc. Translation: The Process • Translation is divided into three phases: – Initiation – Elongation – Termination
    49. 49. © 2010 Pearson Education, Inc. Initiation • Initiation brings together: – mRNA – The first amino acid, Met, with its attached tRNA – Two subunits of the ribosome • The mRNA molecule has a cap and tail that help it bind to the ribosome. Blast Animation: Translation
    50. 50. Start of genetic message Tail End Cap Figure 10.17
    51. 51. © 2010 Pearson Education, Inc. • Initiation occurs in two steps: – First, an mRNA molecule binds to a small ribosomal subunit, then an initiator tRNA binds to the start codon. – Second, a large ribosomal subunit binds, creating a functional ribosome.
    52. 52. Initiator tRNA mRNA Start codon Met P site Small ribosomal subunit A site Large ribosomal subunit Figure 10.18
    53. 53. © 2010 Pearson Education, Inc. Elongation • Elongation occurs in three steps. – Step 1, codon recognition: – the anticodon of an incoming tRNA pairs with the mRNA codon at the A site of the ribosome.
    54. 54. © 2010 Pearson Education, Inc. – Step 2, peptide bond formation: – The polypeptide leaves the tRNA in the P site and attaches to the amino acid on the tRNA in the A site – The ribosome catalyzes the bond formation between the two amino acids
    55. 55. © 2010 Pearson Education, Inc. – Step 3, translocation: – The P site tRNA leaves the ribosome – The tRNA carrying the polypeptide moves from the A to the P site Animation: Translation
    56. 56. Figure 10.19-1 mRNA P site Polypeptide ELONGATION Codon recognition A site Codons Anticodon Amino acid
    57. 57. mRNA P site Peptide bond formation Polypeptide ELONGATION Codon recognition A site Codons Anticodon Amino acid Figure 10.19-2
    58. 58. New peptide bond mRNA movement mRNA P site Translocation Peptide bond formation Polypeptide ELONGATION Codon recognition A site Codons Anticodon Amino acid Figure 10.19-3
    59. 59. New peptide bond Stop codon mRNA movement mRNA P site Translocation Peptide bond formation Polypeptide ELONGATION Codon recognition A site Codons Anticodon Amino acid Figure 10.19-4
    60. 60. © 2010 Pearson Education, Inc. Termination • Elongation continues until: – The ribosome reaches a stop codon – The completed polypeptide is freed – The ribosome splits into its subunits
    61. 61. © 2010 Pearson Education, Inc. Review: DNA→ RNA→ Protein • In a cell, genetic information flows from DNA to RNA in the nucleus and RNA to protein in the cytoplasm.
    62. 62. Transcription RNA polymerase mRNA DNA Intron Nucleus Figure 10.20-1
    63. 63. Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing Figure 10.20-2
    64. 64. Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing tRNA Amino acid Amino acid attachment EnzymeATP Figure 10.20-3
    65. 65. Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing tRNA Amino acid Amino acid attachment EnzymeATP Initiation of translation Ribosomal subunits Figure 10.20-4
    66. 66. Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing tRNA Amino acid Amino acid attachment EnzymeATP Initiation of translation Ribosomal subunits Elongation Anticodon Codon Figure 10.20-5
    67. 67. Transcription RNA polymerase mRNA DNA Intron Nucleus mRNA Intron Tail Cap RNA processing tRNA Amino acid Amino acid attachment EnzymeATP Initiation of translation Ribosomal subunits Elongation Anticodon Codon Termination Polypeptide Stop codon Figure 10.20-6
    68. 68. © 2010 Pearson Education, Inc. • As it is made, a polypeptide: – Coils and folds – Assumes a three-dimensional shape, its tertiary structure • Several polypeptides may come together, forming a protein with quaternary structure.
    69. 69. © 2010 Pearson Education, Inc. • Transcription and translation are how genes control: – The structures – The activities of cells
    70. 70. © 2010 Pearson Education, Inc. Mutations • A mutation is any change in the nucleotide sequence of DNA. • Mutations can change the amino acids in a protein. • Mutations can involve: – Large regions of a chromosome – Just a single nucleotide pair, as occurs in sickle cell anemia
    71. 71. © 2010 Pearson Education, Inc. Types of Mutations • Mutations within a gene can occur as a result of: – Base substitution, the replacement of one base by another – Nucleotide deletion, the loss of a nucleotide – Nucleotide insertion, the addition of a nucleotide
    72. 72. Normal hemoglobin DNA mRNA Normal hemoglobin Mutant hemoglobin DNA mRNA Sickle-cell hemoglobin Figure 10.21
    73. 73. © 2010 Pearson Education, Inc. • Insertions and deletions can: – Change the reading frame of the genetic message – Lead to disastrous effects
    74. 74. © 2010 Pearson Education, Inc. Mutagens • Mutations may result from: – Errors in DNA replication – Physical or chemical agents called mutagens
    75. 75. © 2010 Pearson Education, Inc. • Although mutations are often harmful, they are the source of genetic diversity, which is necessary for evolution by natural selection.
    76. 76. mRNA and protein from a normal gene (a) Base substitution Figure 10.22a
    77. 77. Deleted (b) Nucleotide deletion mRNA and protein from a normal gene Figure 10.22b
    78. 78. mRNA and protein from a normal gene Inserted (c) Nucleotide insertion Figure 10.22c
    79. 79. © 2010 Pearson Education, Inc. VIRUSES AND OTHER NONCELLULAR INFECTIOUS AGENTS • Viruses exhibit some, but not all, characteristics of living organisms. Viruses: – Possess genetic material in the form of nucleic acids – Are not cellular and cannot reproduce on their own.
    80. 80. © 2010 Pearson Education, Inc. Bacteriophages • Bacteriophages, or phages, are viruses that attack bacteria. Animation: Phage T2 Reproductive Cycle
    81. 81. Protein coat DNA Figure 10.24
    82. 82. Figure 10.24
    83. 83. © 2010 Pearson Education, Inc. • Phages have two reproductive cycles. (1) In the lytic cycle: – Many copies of the phage are made within the bacterial cell, and then – The bacterium lyses (breaks open)
    84. 84. © 2010 Pearson Education, Inc. (2) In the lysogenic cycle: – The phage DNA inserts into the bacterial chromosome and – The bacterium reproduces normally, copying the phage at each cell division
    85. 85. Bacterial cell Head Tail Tail fiber DNA of virus Bacteriophage (200 nm tall) Colorized TEM Figure 10.25
    86. 86. © 2010 Pearson Education, Inc. Plant Viruses • Viruses that infect plants can: – Stunt growth – Diminish plant yields – Spread throughout the entire plant Animation: Phage T4 Lytic Cycle Animation: Phage Lambda Lysogenic and Lytic Cycles
    87. 87. Phage Phage DNA Phage injects DNA Phage attaches to cell. Bacterial chromosome (DNA) Phage DNA circularizes. Phages assemble OR New phage DNA and proteins are synthesized. LYTIC CYCLE Cell lyses, releasing phages. Figure 10.26-1
    88. 88. Phage Phage DNA Phage injects DNA Phage attaches to cell. Bacterial chromosome (DNA) Phage DNA circularizes. Phages assemble OR New phage DNA and proteins are synthesized. LYTIC CYCLE Cell lyses, releasing phages. LYSOGENIC CYCLE Phage DNA is inserted into the bacterial chromosome. Many cell divisions Prophage Occasionally a prophage may leave the bacterial chromosome. Lysogenic bacterium reproduces normally, replicating the prophage at each cell division. Figure 10.26-2
    89. 89. Phage Phage DNA Phage injects DNA Phage attaches to cell. Bacterial chromosome (DNA) Phage DNA circularizes.Phages assemble New phage DNA and proteins are synthesized. LYTIC CYCLE Cell lyses, releasing phages. Figure 10.26a
    90. 90. Phage DNA Phage injects DNA Phage attaches to cell. Bacterial chromosome (DNA) Phage DNA circularizes. LYSOGENIC CYCLE Many cell divisions Prophage Occasionally a prophage may leave the bacterial chromosome. Lysogenic bacterium reproduces normally, replicating the prophage at each cell division. Phage DNA is inserted into the bacterial chromosome. Phage Figure 10.26b
    91. 91. Phage lambda E. coli Figure 10.26c
    92. 92. © 2010 Pearson Education, Inc. • Viral plant diseases: – Have no cure – Are best prevented by producing plants that resist viral infection
    93. 93. Tobacco mosaic virus RNA Protein Figure 10.27
    94. 94. Figure 10.27b
    95. 95. Tobacco mosaic virus RNA Protein Figure 10.27a
    96. 96. © 2010 Pearson Education, Inc. Animal Viruses • Viruses that infect animals are: – Common causes of disease – May have RNA or DNA genomes • Some animal viruses steal a bit of host cell membrane as a protective envelope.
    97. 97. Protein coat RNA Protein spike Membranous envelope Figure 10.28
    98. 98. © 2010 Pearson Education, Inc. • The reproductive cycle of an enveloped RNA virus can be broken into seven steps. Animation: Simplified Viral Reproductive Cycle
    99. 99. Protein coat mRNA Protein spike Plasma membrane of host cell Envelope Template New viral genomeNew viral proteins Exit VirusViral RNA (genome) Viral RNA (genome) Entry Uncoating Assembly RNA synthesis by viral enzyme RNA synthesis (other strand) Protein synthesis Figure 10.29
    100. 100. Protein coat Protein spike Plasma membrane of host cell Envelope Virus Viral RNA (genome) Viral RNA (genome) Entry Uncoating RNA synthesis by viral enzyme Figure 10.29a
    101. 101. mRNA Template New viral genome New viral proteins Exit Assembly RNA synthesis (other strand) Protein synthesis Figure 10.29b
    102. 102. © 2010 Pearson Education, Inc. HIV, the AIDS Virus • HIV is a retrovirus, an RNA virus that reproduces by means of a DNA molecule. • Retroviruses use the enzyme reverse transcriptase to synthesize DNA on an RNA template. • HIV steals a bit of host cell membrane as a protective envelope.
    103. 103. Envelope Reverse transcriptase Surface protein Protein coat RNA (two identical strands) Figure 10.31
    104. 104. © 2010 Pearson Education, Inc. • The behavior of HIV nucleic acid in an infected cell can be broken into six steps. Animation: HIV Reproductive Cycle Blast Animation: AIDS Treatment Strategies
    105. 105. Reverse transcriptase HIV (red dots) infecting a white blood cell DNA strand Chromosomal DNA Cytoplasm Nucleus Provirus RNA Viral RNA Double stranded DNA Viral RNA and proteins SEM Figure 10.32
    106. 106. Reverse transcriptase DNA strand Chromosomal DNA Cytoplasm Nucleus Provirus RNA Viral RNA Double stranded DNA Viral RNA and proteins Figure 10.32a
    107. 107. © 2010 Pearson Education, Inc. • AIDS (acquired immune deficiency syndrome) is: – Caused by HIV infection and – Treated with drugs that interfere with the reproduction of the virus
    108. 108. HIV (red dots) infecting a white blood cell SEM Figure 10.32b
    109. 109. Part of a T nucleotide Thymine (T) AZT Figure 10.33
    110. 110. © 2010 Pearson Education, Inc. Viroids and Prions • Two classes of pathogens are smaller than viruses: – Viroids are small circular RNA molecules that do not encode proteins – Prions are misfolded proteins that somehow convert normal proteins to the misfolded prion version
    111. 111. © 2010 Pearson Education, Inc. • Prions are responsible for neurodegenerative diseases including: – Mad cow disease – Scrapie in sheep and goats – Chronic wasting disease in deer and elk – Creutzfeldt-Jakob disease in humans
    112. 112. Figure 10.34
    113. 113. Evolution Connection: Emerging Viruses • Emerging viruses are viruses that have: – Appeared suddenly or – Have only recently come to the attention of science © 2010 Pearson Education, Inc.
    114. 114. © 2010 Pearson Education, Inc. • Avian flu: – Infects birds – Infected 18 people in 1997 – Since has spread to Europe and Africa infecting 300 people and killing 200 of them
    115. 115. © 2010 Pearson Education, Inc. • If avian flu mutates to a form that can easily spread between people, the potential for a major human outbreak is significant.
    116. 116. Figure 10.35
    117. 117. © 2010 Pearson Education, Inc. • New viruses can arise by: – Mutation of existing viruses – Spread to new host species
    118. 118. Figure 10.UN1
    119. 119. Figure 10.UN2
    120. 120. Polynucleotide Phosphate group Nucleotide Sugar DNA Nitrogenous base Nitrogenous base Number of strands Sugar DNA RNA Ribose Deoxy- ribose C G A T C G A U 12 Figure 10.UN3
    121. 121. Polynucleotide Phosphate group Nucleotide Sugar DNA Nitrogenous base Figure 10.UN3a
    122. 122. Nitrogenous base Number of strands Sugar DNA RNA RiboseDeoxyribose C G A T C G A U 12 Figure 10.UN3b
    123. 123. New daughter strand Parental DNA molecule Identical daughter DNA molecules Figure 10.UN4
    124. 124. Polypeptide TRANSLATIONTRANSCRIPTION mRNA DNA Gene Figure 10.UN5
    125. 125. Growing polypeptide mRNA Codons Large ribosomal subunit tRNA Small ribosomal subunit Anticodon Amino acid Figure 10.UN6
    126. 126. Figure 10.UN7

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