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Figure 10.22 PowerPoint PPT Presentation


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Figure 10.22. VIRUSES: GENES IN PACKAGES. Viruses Components Infection cycle 3. DNA, RNA viruses 4. Uses of viruses. Components of a virus (phage). 1. Protein coat = capsid 2.genetic material DNA or RNA 3. enzyme. Components of a virus. Membranous envelope. envelope capsid

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Figure 10.22

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Figure 10.22


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VIRUSES: GENES IN PACKAGES

Viruses

Components

Infection cycle

3. DNA, RNA viruses

4. Uses of viruses


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Components of a virus (phage)

1. Protein coat = capsid

2.genetic material

DNA or RNA

3. enzyme


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Components of a virus

Membranousenvelope

  • envelope

  • capsid

  • genetic material

    • Ex. flu viruses

RNA

Proteincoat

Glycoprotein spike

Figure 10.18A


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  • Phage reproductive cycle

Phage DNA directs host cell to make more phage DNA and protein parts. New phages assemble.

Phage attaches to bacterial cell.

Phage injects DNA.

Cell lyses and releases new phages.


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Viral DNA may become part of the host chromosome

Phage

Attachesto cell

Bacterialchromosome

Phage DNA

Cell lyses,releasing phages

Phage injects DNA

Many celldivisions

Occasionally a prophagemay leave the bacterialchromosome

LYTIC CYCLE

LYSOGENIC CYCLE

Phagesassemble

Phage DNAcircularizes

Lysogenic bacteriumreproduces normally,replicating the prophageat each cell division

Prophage

OR

New phage DNA andproteins are synthesized

Phage DNA inserts into the bacterialchromosome by recombination


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Glycoprotein spike

VIRUS

Protein coat

Viral RNA(genome)

Envelope

Plasmamembraneof hostcell

Entry

1

Uncoating

2

  • Viruses redirect the host cell machinery to make more viruses

  • Some animal viruses steal a bit of the host cell’s membrane

Viral RNA(genome)

RNA synthesisby viral enzyme

3

Proteinsynthesis

RNA synthesis(other strand)

5

4

mRNA

Template

New viral

genome

Newviral protein

Newviral proteins

Assembly

6

Exit

7

Figure 10.18B


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Plant viruses are serious agricultural pests

  • Most plant viruses have RNA

    • Example: tobacco mosaic disease

Protein

RNA

Figure 10.19


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  • The deadly Ebola virus causes hemorrhagic fever

    • Each virus is an enveloped thread of protein-coated RNA

  • Hantavirus is another enveloped RNA virus

  • SARS - coronavirus

  • Avian flu

Figure 10.20A, B


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  • HIV, seen here attacking a white blood cell

Figure 10.22


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  • HIV is a retrovirus


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Invasion of T cell by HIV


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  • HIV infection

Figure 10.22x1


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  • AIDS quilt

Figure 10.22x2


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Uses of Viruses

  • Pest control

  • Vaccines

  • Anti-cancer treatment

  • Gene therapy


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Anti-cancer viruses

Makes use of viral ability to enter only cells of one type

Allows targeting of therapy to tumor cells

Enables identification of small tumor sites


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Coming soon to your local pharmacy!


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Other parasitic particles

  • Viroids - infectious RNA (no capsid)

  • Prions - infectious protein

    • Cellular PrP, prion PrP

    • Spongiform encephalopathies cause neural degeneration


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