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Viruses Flashcards

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Biology 101 flashcards
1
Q

viruses are obligate intracellular parasites because

A
  • they cannot reproduce without a host
  • not considered to be living
  • virus genome more similar to host genome than other virus genomes
  • almost identical to host genome in some groups
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2
Q

Iwanoski

A

first to isolate virus in 1892

tobacco mosaic virus

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3
Q

virus classifications

A
  • host range
  • size
  • structure
  • virus life cycle
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4
Q

host range

A
  • viruses infect all organisms

- usually adapted to one species or related species

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5
Q

size

A

smaller than ribosomes

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6
Q

structure

A
  • nucleic acid
  • capsid
  • animal viruses have envelope outside capsid
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7
Q

nucleic acid in viruses

A

can have DNA or RNA
single or double strand
1 piece or more than 1 piece

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8
Q

capsid

A

protein container enclosing nucleic acid

  • helical, rod, tobacco mosaic virus
  • polyhedral, 20 sided, adenovirus, cold virus
  • complex, tail, head, sheath, bacteriophage
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9
Q

animal virus external envelope

A

-outside capsid
-derived from host membrane
HIV, flu
-envelope allows virus to merge with membrane when entering and leaving the host

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10
Q

virus life cycle

A
  1. virus binds host membrane
  2. virus releases nucleic acid into host cell
  3. new virus nucleic acids and virus proteins synthesized in host
  4. new capsids assemble around nucleic acids
  5. new viruses released from host cell
    - some kill host cell as new viruses are released
    - enveloped virus- leaves host cell without killing host
    cell
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11
Q

3 virus groups

A
  1. DNA viruses (bacteriophages)
  2. RNA viruses
  3. retroviruses (RNA)
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12
Q

Bacteriophage

A

DNA virus
infects E. coli
viral DNA injected into host
lytic and lysogenic life cycles
more bacteriophages on body than all other cell types combined
ex: Corynebacterium, Vibrio, Clostridium botulinum

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13
Q

lytic cycle

A

virulent

produces new viruses and kills host and then infects other cells

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14
Q

lysogenic life cycle

A

viral DNA incorporated into host DNA and replicated with host DNA as host divides
all resulting cells contain viral DNA and express the viral toxin
the bacteriophage infection makes non-pathogenic bacterial disease causing toxins cause symptoms
more bacteriophages on body than all other cell types combined

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15
Q

RNA virus

A

8 RNA strands

influenza

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16
Q

RNA virus enzyme

A 
RNA replicase (RNA dependent RNA polymerase)
copies virus RNA into more virus RNA
NO DNA and NO transcription- genetic information already in RNA form
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17
Q

RNA virus presentation

A

respiratory infection often followed by secondary bacterial infections; pneumonia
spread by respiratory droplets and fomites (contaminated objects)

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18
Q

influenza envelope

A

2 surface spike protein patterns (H and N)

spikes allow virus to bind, enter and exit host

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19
Q

spike variation determines______

A

capsid antigen characteristics (A, B or C)

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20
Q

antigenic shift

A

recombines RNA from human, pig or bird flu strains
RNA from different species combined into new influenza virus in host
preformed antibodies may still function
most severe

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21
Q

antigenic drift

A

variation from random point mutations
only a few amino acids changed
preformed antibodies may still function
not as severe

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22
Q

influenza A

A

most common, most severe form
cause of pandemics in 1918, 1957, 1968, 1977
Spanish flu

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23
Q

avian flu

A

H7H9, H5N1, H7N7
infection in poultry in Asia and Africa
60% fatality rate

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24
Q

H3N2

A

human flu

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25
Q

H1N1, H2N2

A

swine flu

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26
Q

Retrovirus

A

2 RNA strands

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27
Q

Retrovirus enzyme

A

reverse transcriptase

copies RNA into DNA

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28
Q

HIV

A

Human Immunodeficiency Virus

  1. binds CD4 receptors on T4 helper cells and macrophages
    • structure changes to reduce antibody response
  2. moves inside T4 cells
    • RNA converted to DNA by reverse transcriptase
    • virus DNA inserts into host DNA
    • may remain inactive but usually produces and releases new viruses that infect other cells
  3. T4 count falls
    • body cannot produce enough new T4 cells
    • indicates onset of AIDS
  4. HIV destroys immune system and death results from secondary infection
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29
Q

secondary infection/ diseases related to HIV

A

Pneumocystis carinii
Toxoplasma
Mycobacterium tuberculosis
Karposi’s sarcoma

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30
Q

HAART

A

Highly Active Antiretroviral Therapy

drug cocktails

31
Q

drug cocktail effects

A

reduce virus to low levels
maintain T4 helper cell number
reduce resistance of viruses to treatment

32
Q

treatment targets on HIV

A
  • interfere with reverse transcriptase
  • fusion inhibitors
  • integrase inhibitors
  • protease inhibitors
  • block virus assembly
33
Q

treatments that interfere with reverse transcriptase

A

inhibit DNA synthesis from RNA

34
Q

AZT

A

mimics thymine nucleotides

produces non-functional DNA

35
Q

fusion inhibitors

A

prevents virus entry into host membrane

36
Q

protease inhibitors

A

prevent modification of HIV proteins

37
Q

integrase inhibitors

A

prevent HIV DNA from inserting into host DNA

38
Q

HIV treatment drawbacks

A

high cost
toxic side effects
may not completely remove virus`

39
Q

why some HIV is a “long term non progress or”

A

weaker virus

abnormal receptors on T4 cells

40
Q

Hepatitis

A

targets liver
fecal/oral transmission
many strains, syndromes, outcomes

41
Q

Hepatitis A

A 
infectious hepatitis
RNA
contagious before symptoms appear
survives for days on surfaces
resistant to bleach
1/3 Americans have antibodies form Hep A
42
Q

Hepatitis A passive vaccine

A

effective within 2 weeks of exposure

protection lasts six months

43
Q

Hepatitis A active vaccine

A

(developed in) 1995 (?)

44
Q

Hepatitis B

A

chronic hepatitis
liver cancer
DNA
transmission similar to HIV- infected blood, blood products, IV drug use, unsafe sex

45
Q

Hepatitis B active vaccine

A

for newborns and children

46
Q

Hepatitis B passive vaccine

A

reduces severity of infection after exposure to hep B

47
Q

Hepatitis C

A 
chronic
RNA
no vaccine
similar transmission to HIV
higher fatality rate than HIV
main reason for liver transplant
48
Q

Rhabdovirus

A

rabies

ssRNA

49
Q

rhabdovirus reservoir

A

mammals (not rodents)

50
Q

rhabdovirus transmission

A

bites

travels along nerves to brain

51
Q

rhabdovirus infection

A

40 day incubation time
causes encephalitis
usually fatal within a few days of onset of symptoms

52
Q

hydrophobia

A

painful muscle spasms from swallowing water

contractions of jaw muscles

53
Q

furious rabies

A

biting maintains virus in animal populations

54
Q

polio virus

A

ssRNA
poliomylelitis strains 1, 2, 3
human only host
inhibits motor neurons in cord

55
Q

polio transmission

A

fecal/oral
stable in swimming pools, lakes, drinking water, food
only 1% becomes paralytic

56
Q

Salk vaccine

A

first active vaccine
antigens for all 3 polio strains
inactive virus so requires boosters
used to vaccinate children

57
Q

Sabin vaccine

A

oral vaccine
attentuated (living) providing long lasting immunity
80 polio cases in secondary contacts since 1980

58
Q

post polio syndrome

A

muscle weakness that occurs later in life as nerves become inhibited

59
Q

herpes simplex 1

A

oral herpes

60
Q

herpes simplex 2

A

genital herpes

61
Q

human papilloma virus

A

many strains

some cause cervical cancer

62
Q

Ebola

A

Africa
fruit bat reservoir
incurable
90% fatality rate

63
Q

west Nile virus

A

bird reservoir
mosquito vector
f

64
Q

Viroids

A

infectious RNA molecules
only infect plants
potato spindle tuber, cadang/cadang

65
Q

prions

A

infectious proteins that infect brain

no cure

66
Q

prion infection

A

eating meat contaminated with CNS tissue
slow acting with long incubation time
not destroyed by high heat

67
Q

prion effect

A

convert normal proteins in brain to prions

prions are a misfiled form of normal protein (beta sheet, prion PrP)

68
Q

scrapies

A

prion in sheep

69
Q

bovine spongiform encephalopathy

A

mad cow disease

sheep to cow, cow to cow, cow to human

70
Q

Creutzfeldt Jacob disease

A

human for of mad cow

71
Q

Kuru

A

related to cannabalism

72
Q

chronis wasting disease

A

deer and elk

73
Q

Viruses and cancer

A

cause 20-25% of cancers
HIV- Karposi’s sarcoma
HPV- cervical cancer

Microbiology (27 decks)

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