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Micro > Chapter 8: Viruses > Flashcards

Chapter 8: Viruses Flashcards

1
Q

Virus

A

genetic element that cannot replicate independently of a living (host) cell

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2
Q

Virus particle

A

virion
extracellular form of a virus
exists outside host and facilitates transmission from one host cell to another

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3
Q

infection

A

entry of viral DNA into host cell

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4
Q

Capsid

A

the protein shell that surrounds the genome of a virus particle

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5
Q

Naked virus

A

have no other layers than a capsid
- ie most bacterial viruses

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6
Q

Enveloped virus

A

have outer layer consisting of a phospholipid bilayer (from host cell membrane) and viral proteins
- ie many animal viruses

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7
Q

Nucleocapsid

A

nucleic acid + protein capsid

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8
Q

virulent infection

A

lytic
- replicates and destroys host

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9
Q

lysogenic infection

A

host cell genetically altered because viral genome becomes part of host genome

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10
Q

capsomere

A

individual protein molecules arranged in a precise and highly repetitive pattern around the nucleic acid making up the capsid

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11
Q

icosahedral

A

spherical viruses
most efficient arrangement of subunits in a closed shell
requires fewest capsomeres
- ie. Ebola, human papillomavirus

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12
Q

Helical

A

rod-shaped viruses
length of virus determined by length of nucleic acid
width of virus determined by size and packaging of capsomeres
- ie. tobacco mosaic virus, Human rhinovirus

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13
Q

complex

A

ie. bacteriophage

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14
Q

lysozyme

A

makes holes in cell wall to allow nucleic acid entry
also lyses bacterial cell to release new virions

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15
Q

neuraminidases

A

destroy glycoproteins and glycolipids
allows liberation of viruses from cell

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16
Q

nucleic acid polymerases

A

RNA-replicases + reverse transcriptase

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17
Q

Phases of viral replication in a permissive host

A

attachment - penetration - synthesis - assembly - release

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18
Q

virus replication growth curve:

A

one-step growth curve
- numbers increase when cell bursts

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19
Q

Eclipse

A

genome replicated and proteins translated

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20
Q

maturation

A

packaging of nucleic acids in capsids

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21
Q

latent period

A

eclipse + maturation

22
Q

release

A

cell lysis, budding, or excretion

23
Q

burst size

A

number of virions released

24
Q

lawns

A

hosts in liquid medium or spread on agar and inoculated with viruses
- best for bacterial viruses

25
Q

tissue culture

A

animal organ in culture medium
- used for animal viruses

26
Q

titer

A

number of infectious units per volume

27
Q

plaque assay

A

plaques are clear zones that develop on lawns of host cells where successful viral infection occurs
(where cells are being lysed)

28
Q

plating efficiency

A

number of plaque-forming units is always lower than direct counts by electron microscopy
- efficiency of infection is usually much lower than 100%

29
Q

Attachment

A

requires complementary receptors on the surface of a susceptible host for its infecting virus
- proteins, carbs, glycoproteins, lipids, lipoproteins, or other cell structures

30
Q

penetration

A

capsid left outside cell, viral genome and viral proteins (some viruses) enter host

31
Q

T4 penetration

A

-attach via tail fibers interactions with E. coli LPS layer
-fibers retract and tail pins contact cell wall
-T4 lysozyme forms small pore in peptidoglycan
-tail sheath contracts, viral DNA enters cytoplasm
-capsid stays outside

32
Q

restriction endonucleases

A

enzymes that cleave foreign DNA at specific sites
-specific for dsDNA (ssDNA/RNA unaffected)

33
Q

modification

A

modification of cells own DNA at restriction enzyme recognition sites prevents cleavage of own DNA
- ie base substitution

34
Q

circular permutation

A

same genes arranged in different orders
- features of tmany virus genomes

35
Q

terminally redundant

A

some DNA sequences duplicated on both ends

36
Q

early proteins

A

enzymes needed for DNA replication and transcription

37
Q

middle and late proteins

A

head and tail proteins and enzymes required to liberate mature phage particles

38
Q

virulent

A

viruses always lyse and kill host after infection

39
Q

temperate

A

viruses replicate their genome in tandem with host genome and without killing the host, establishing long-term, stable relationship

40
Q

lysogen

A

host cell that harbors temperate virus

41
Q

lysogeny

A

most viral genes are not transcribed
- viral genome is replicated with host chromosome and passed to daughter cells

42
Q

prophage

A

viral DNA

43
Q

transduction

A

packaging of host chromosomal genes and transfer to new host

44
Q

cl protein

A

the lambda repressor
- causes repression of lambda lytic events

45
Q

cro repressor

A

controls activation of lytic events

46
Q

latent infection

A

viral DNA exists in host genome and virions are not produced; host cell is unharmed unless/until virulence is triggered

47
Q

persistent infection

A

release of virions from host cell by budding does not result in cell lysis
- infected cell remains alive and continues to produce virus

48
Q

transformation

A

conversion of normal cell into tumor cell

49
Q

retroviruses

A

RNA virus that replicate through a DNA intermediate
-ie HIV

50
Q

gag

A

encode structural proteins in retrovirus

51
Q

pol

A

encode reverse transcriptase and integrase in retrovirus

52
Q

env

A

encode envelope proteins in retrovirus

Micro (9 decks)

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