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Biology 2 > Ch 27: Viruses > Flashcards

Ch 27: Viruses Flashcards

0
Q

Virion

A
  • Single virus particle outside of a
    cell
  • not alive or dead
  • relies on living cells for replication
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1
Q

Nature of Viruses

A
  • All viruses have same basic structure
    -Nucleic acid core surrounded by
    Capsid
    -DNA or RNA
    - Circular or Linear
  • No cytoplasm: not a cell
    -no ribosomes
  • Classified by genome
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2
Q

Capsid

A

Nearly all viruses form protein sheath around nucleic acid core
-composed of 1 to a few proteins

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3
Q

Stores Enzymes

A

Some viruses store specialized emzymes not found in host

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4
Q

Shapes

A

2 simple shapes

- helical: rodlike/threadlike
- Icosahedral: soccer ball shape
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5
Q

Complex shapes

A

T-even bacteria - 2 fold symmetry
-bacteriophage are viruses that
infect bacteria
Pox viruses -multilayered capsids

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6
Q

Viral Hosts

A

Infra cellular parasites in every kind of organism investigated.

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7
Q

Host Range (specific invasion)

A

-Types of organisms infected
-each type of virus has limited
host range
-Tissue tropism: inside a host virus
may only infect a certain tissues
-Viruses can remain dormant for
years
- chicken pox can reemerge as
shingles

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8
Q

Replication

A

Infecting can be thought of set of instructions

  • viral genome tricks host into making more viruses
  • viruses can only reproduce inside cells.
  • can’t synthesize proteins- no ribosomes
  • virus hijacks cell’s transcription and translation machineries to express early genes, middle genes, & late genes.
  • end result is assembly & release of viruses
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9
Q

Viral Genomes

A 
Vary greatly in both type of Nucleic acid and number of strands
- Most RNA viruses are single 
  stranded
     - replicated in host cell's 
       cytoplasm
     - replication in cytosol is error 
       prone
Most DNA viruses double stranded
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10
Q

RNA Viruses

A
  • Positive strand virus: viral RNA serves as mRNA
  • Neg strand: genome is complementary to viral mRNA
  • Retroviruses: employ reverse transcriptase to reverse transcribe viral RNA to DNA
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11
Q

Bacteriophage

A
  • Viruses that infect bacteria
  • Diverse and united only by bacterial hosts
  • Also found in archae
    • diff from bacterial viruses
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12
Q

HIV

A 
- Causes Acquired Immune  
   Deficiency Syndrome (AIDS)
- 1st reported in 81 but originated 
   from Africa in 50s
- Some people resistant to HIV; 
  others have HIV but don't get AIDS
- Targets CD4+ cells, mainly T cells
- Host usually dies from infection 
  the body would normally fight off.
- Clinical symptoms usually appear 
  after 8-10 year latent period
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13
Q

CCR5 Receptor

A
  • Used by HIV May have been used
    by smallpox.
  • individuals without receptors are
    resistant
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14
Q

HIV Testing

A
  • not a test for circulating virus; test for presence of antibodies against HIV.
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15
Q

HIV Infection Cycle

A 
Attachment
   - viral gp120 attaches to CD4     
     protein on macrophages and
     CD4 cells.
Entry
    -through fusion pore
    - Coreceptors like CCR5 affect
      likelihood of entry.
Replication
    -converts RNA to DNA which     
     incorporates into host genome
Assembly
   -makes virus copies
Release
   -new virus exits by budding
16
Q

AIDS Treatments

A 
- FDA lists 35 antiretroviral drugs 
  used in AIDS therapy
- Targets 4 aspects of HIV life cycle
     -viral entry, genome replication,
      Integration of viral DNA, and 
      maturation of HIV proteins
- Vaccine development 
  unsuccessful
17
Q

Influenza

A 
- One of most lethal viruses in    
  human history
- Enveloped animal viruses
     -Type A: serious epidemics in 
       humans & other animals
     - Type B & C: mild human 
        infections
H (hemagglutinin): 
     -aids virus in gaining access to 
      cell interior.
N (neuraminidase):
     -helps daughter viruses break 
      free of host cell once virus 
       replication is done.
18
Q

Origin

A

New strains of flu tend to come from Far East.
-virus hosts are ducks, cows,
chickens, etc

19
Q

Emerging Viruses

A
  • Viruses that extend their host range
  • Often deadly to new host
  • Considerable threat in aviation age
  • Hantavirus
    • causes deadly pneumonia
    • nat. host is deer mouse
20
Q

Ebola

A

Causes severe hemorrhagic fever
Among most lethal infectious diseases
Host is unknown

21
Q

SARS

A
  • Severe Acute Respiratory Syndrome
  • Caused by coronavirus
  • Host is civet (weasel-like)
  • Mutation rate low compared to HIV
  • Vaccine currently being devel.
22
Q

Viruses and Cancer

A

Viruses may contribute to about 15% of human cancers by altering the growth property of human cells

  • triggers expression of oncogenes
  • disrupt cell cycle
23
Q

Prions

A
  • Proteinaceous infectious particles
  • Proteins that infect brain & cause
    spongy appearance.
    • mad cow disease
    • scabies in sheep
    • creutzfeldt: Jacob disease in
      humans (CJD)
24
Q

Viroids

A 
Tiny naked mols. of circular RNA
Causes disease in plants
Autonomously replicate.
    -info appears to be in 3-D 
     structure
25
Q

AIDS

A
  • First recognized in 1980s.
  • > 33 mil people with HIV
  • Came from SIV Simian immunodeficiency Virus- in 36 primate species
26
Q

Bacteriophage Reprod:

Lytic cycle

A 
1) Attachment or absorption:
    attaches to part of cell wall
2) Penetration: 
    injection of viral DNA
3) Synthesis: 
    protein & Nucleic acid
4) Assembly:
    spont. assembly of capsid & 
    enzyme to insert DNA
5) Release:
    Lysis of cell
27
Q

Bacteriophage Reprod:

Lysogenic cycle

A
  • Between penetration & synthesis

1) Integration of genome leads to…
2) Prophage:
allows virus replic. w/ host
cell’s DNA as host cell divides
3) Induction:
Prophage exits bacterial
chromosome, viral genes are
expressed

Biology 2 (7 decks)

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