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bio > a2.3- viruses > Flashcards

a2.3- viruses Flashcards

1
Q

structural features common to viruses [8]

A
  • non-living (no metabolic machinery of their own)
  • small
  • fixed size
  • nucleic acid (DNA or RNA) as genetic material
  • capsid made of protein
  • no cytoplasm
  • no/few enzymes
  • relies on a host cell to replicate
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2
Q

lytic cycle mechanism

A
  1. attaches
    - binds to receptor that allows it to dock there
    - inject genetic material
  2. makes copies of the virus
  3. sm copies- cell membrane explodes
  4. infect other organisms
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3
Q

lytic cycle examples

A

bacteriophage lambda of E. Coli

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4
Q

lysogenic cycle mechanism

A
  1. attachment
  2. entry of genetic material
  3. integration
  4. cell division
    - DNA becomes integrated into the bacterial DNA molecule
    - daughter cell continues the process
    - usually naked
    - temperate (wont try to kill the host yet)
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5
Q

lysogenic cycle example

A

bacteriophage lambda of E. Coli

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6
Q

convergent evolution

A
  • progressive hypothesis
  • originated from simpler genetic elements
  • gradually acquired the ability to infect and replicate within host cells
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7
Q

evidence of convergent evolution

A
  • matches how there are virus like components in some cells
    eg. retrotransposon/ circular plasmid is simple and can be synthesised
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8
Q

divergent evolution

A
  • regressive hypothesis
  • originated from more complex cellular organisms that underwent a process of degeneration
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9
Q

evidence for divergent evolution

A
  • some viruses share genome similar to cellular organisms
  • show variation in complexity and self-reliance
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10
Q

reasons for rapid evolution [4]

A
  1. short generation time
  2. high mutation rates- often do not proofread
  3. increases rate of survival: evade defence mechanism of the host cell
  4. high natural selection pressure
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11
Q

rapid evolution examples [2]

A
  1. influenza
    - RNA replicase doesnt proofread + often makes errors
  2. HIV
    - reverse transcriptase (rna -> dna) tricks us to use it
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12
Q

antigenic drift

A

as more mutations occur- cant recognise the virus anymore

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13
Q

antigenic shift

A

animal → human

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14
Q

consequences for treating diseases caused by rapidly evolving viruses

A

develop immunity to medicine- wont die

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15
Q

what virus cant do lysogenic cycle

A

T7 virus

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16
Q

eg of small and simple virus

A

polio virus

17
Q

eg of large and complex virus

18
Q

expectation for cells in bacteria

A
  • to be self reliant
    EXCEPTION: parasitic bacteria, replicates inside a host cell
19
Q

diversity of structure in viruses [2]

A
  1. diversity of genetic material
  2. enveloped / non-enveloped
20
Q

eg of dna virus [2]

A
  1. smallpox
  2. hepatitis B
21
Q

eg of rna virus [2]

A
  1. corona virus
  2. ebola

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