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Fig. 19-1 Figure 19.1 Are the tiny viruses infecting this E. coli cell alive? 0.5 µm
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RESULTS Extracted sap from tobacco plant with tobacco mosaic disease
Fig. 19-2 RESULTS 1 Extracted sap from tobacco plant with tobacco mosaic disease 2 Passed sap through a porcelain filter known to trap bacteria 3 Rubbed filtered sap on healthy tobacco plants Figure 19.2 What causes tobacco mosaic disease? 4 Healthy plants became infected
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RNA DNA Membranous envelope Head RNA Capsomere DNA Capsid Tail sheath
Fig. 19-3 RNA DNA Membranous envelope Head RNA Capsomere DNA Capsid Tail sheath Capsomere of capsid Tail fiber Glycoprotein Glycoproteins 18 250 nm 70–90 nm (diameter) 80–200 nm (diameter) 80 225 nm Figure 19.3 Viral structure 20 nm 50 nm 50 nm 50 nm (a) Tobacco mosaic virus (b) Adenoviruses (c) Influenza viruses (d) Bacteriophage T4
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18 250 nm RNA Capsomere of capsid (a) Tobacco mosaic virus 20 nm
Fig. 19-3a RNA Capsomere of capsid 18 250 nm Figure 19.3 Viral structure 20 nm (a) Tobacco mosaic virus
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DNA Capsomere Glycoprotein 70–90 nm (diameter) (b) Adenoviruses 50 nm
Fig. 19-3b DNA Capsomere Glycoprotein 70–90 nm (diameter) Figure 19.3 Viral structure 50 nm (b) Adenoviruses
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Membranous envelope RNA Capsid Glycoproteins 80–200 nm (diameter)
Fig. 19-3c Membranous envelope RNA Capsid Glycoproteins 80–200 nm (diameter) Figure 19.3 Viral structure 50 nm (c) Influenza viruses
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Head DNA Tail sheath Tail fiber 80 225 nm (d) Bacteriophage T4 50 nm
Fig. 19-3d Head DNA Tail sheath Tail fiber 80 225 nm Figure 19.3 Viral structure 50 nm (d) Bacteriophage T4
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VIRUS Entry and uncoating DNA Capsid Transcription and manufacture
Fig. 19-4 VIRUS Entry and uncoating 1 DNA Capsid Transcription and manufacture of capsid proteins 3 2 Replication HOST CELL Viral DNA mRNA Viral DNA Capsid proteins Figure 19.4 A simplified viral reproductive cycle Self-assembly of new virus particles and their exit from the cell 4
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Fig 1 Attachment Figure 19.5 The lytic cycle of phage T4, a virulent phage
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Attachment Entry of phage DNA and degradation of host DNA 1 2
Fig 1 Attachment 2 Entry of phage DNA and degradation of host DNA Figure 19.5 The lytic cycle of phage T4, a virulent phage
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Attachment Entry of phage DNA and degradation of host DNA
Fig 1 Attachment 2 Entry of phage DNA and degradation of host DNA Figure 19.5 The lytic cycle of phage T4, a virulent phage 3 Synthesis of viral genomes and proteins
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Attachment Entry of phage DNA and degradation of host DNA
Fig 1 Attachment 2 Entry of phage DNA and degradation of host DNA Phage assembly Figure 19.5 The lytic cycle of phage T4, a virulent phage 4 Assembly 3 Synthesis of viral genomes and proteins Head Tail Tail fibers
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Attachment Entry of phage DNA and degradation of host DNA Release
Fig 1 Attachment 2 Entry of phage DNA and degradation of host DNA 5 Release Phage assembly Figure 19.5 The lytic cycle of phage T4, a virulent phage 4 Assembly 3 Synthesis of viral genomes and proteins Head Tail Tail fibers
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The phage injects its DNA.
Fig. 19-6 Daughter cell with prophage Phage DNA The phage injects its DNA. Cell divisions produce population of bacteria infected with the prophage. Phage DNA circularizes. Phage Bacterial chromosome Occasionally, a prophage exits the bacterial chromosome, initiating a lytic cycle. Lytic cycle Lysogenic cycle The bacterium reproduces, copying the prophage and transmitting it to daughter cells. The cell lyses, releasing phages. Lytic cycle is induced or Lysogenic cycle is entered Figure 19.6 The lytic and lysogenic cycles of phage λ, a temperate phage Prophage New phage DNA and proteins are synthesized and assembled into phages. Phage DNA integrates into the bacterial chromosome, becoming a prophage.
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Table 19-1 Table 1
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Table 19-1a Table 1
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Table 19-1b Table 1
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Capsid and viral genome enter the cell Capsid
Fig. 19-7 Capsid and viral genome enter the cell Capsid RNA HOST CELL Envelope (with glycoproteins) Viral genome (RNA) Template mRNA Capsid proteins ER Copy of genome (RNA) Glyco- proteins Figure 19.7 The reproductive cycle of an enveloped RNA virus New virus
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Fig. 19-8 Glycoprotein Viral envelope Capsid RNA (two identical strands) Reverse transcriptase HIV Membrane of white blood cell HIV HOST CELL Reverse transcriptase Viral RNA RNA-DNA hybrid 0.25 µm HIV entering a cell DNA NUCLEUS Provirus Chromosomal DNA Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS RNA genome for the next viral generation mRNA New virus New HIV leaving a cell
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Viral envelope Glycoprotein Capsid RNA (two identical strands) Reverse
Fig. 19-8a Glycoprotein Viral envelope Capsid RNA (two identical strands) Reverse transcriptase HOST CELL HIV Reverse transcriptase Viral RNA RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS mRNA New virus
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Membrane of white blood cell HIV HIV entering a cell
Fig. 19-8b Membrane of white blood cell HIV Figure 19.8 The reproductive cycle of HIV, the retrovirus that causes AIDS 0.25 µm HIV entering a cell New HIV leaving a cell
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(a) The 1918 flu pandemic (b) Influenza A H5N1 virus
Fig. 19-9 (a) The 1918 flu pandemic 0.5 µm Figure 19.9 Influenza in humans and other animals For the Discovery Video Emerging Diseases, go to Animation and Video Files. (b) Influenza A H5N1 virus (c) Vaccinating ducks
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(a) The 1918 flu pandemic Fig. 19-9a
Figure 19.9 Influenza in humans and other animals (a) The 1918 flu pandemic
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(b) Influenza A H5N1 virus 0.5 µm Fig. 19-9b
Figure 19.9 Influenza in humans and other animals (b) Influenza A H5N1 virus
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(c) Vaccinating ducks Fig. 19-9c
Figure 19.9 Influenza in humans and other animals (c) Vaccinating ducks
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Fig Figure Viral infection of plants
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Fig a Figure Viral infection of plants
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Fig b Figure Viral infection of plants
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Fig c Figure Viral infection of plants
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Original Prion prion Aggregates of prions New prion Normal protein
Fig Original prion Prion Aggregates of prions New prion Normal protein Figure Model for how prions propagate
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host cell and injects its DNA Phage DNA
Fig. 19-UN1 The phage attaches to a host cell and injects its DNA Phage DNA Bacterial chromosome Prophage Lytic cycle Lysogenic cycle Virulent or temperate phage Destruction of host DNA Production of new phages Lysis of host cell causes release of progeny phages Temperate phage only Genome integrates into bacterial chromosome as prophage, which (1) is replicated and passed on to daughter cells and (2) can be induced to leave the chromosome and initiate a lytic cycle
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Fig. 19-UN2 A B Number of bacteria Number of viruses Time Time
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Fig. 19-UN3
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You should now be able to:
Explain how capsids and envelopes are formed Distinguish between the lytic and lysogenic reproductive cycles Explain why viruses are obligate intracellular parasites Describe the reproductive cycle of an HIV retrovirus Describe three processes that lead to the emergence of new diseases Describe viroids and prions
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