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Medical Microbiology > L 26 - 30 > Flashcards

L 26 - 30 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

True or False: Viruses are obligate intracellular parasites that use host cell translation machinery

A

True

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2
Q

Viral replication yields ___, which are the vehicle for transmission to next host cell

A

Virion

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3
Q

True or False: Viral genome is RNA only and are packaged inside particle

A

False - while genomes of viruses are packaged inside particle, the genome itself can be RNA/DNA

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4
Q

DNA viruses either use host ___ or encode their own

A

polymerases

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5
Q

True or False: (+) SS RNA viruses makes mRNA while – transcription/translation–(-) SS RNA makes polypeptides only

A

False

(+) SS RNA
- polyproteins
- translation

(-) SS RNA
- mRNA
- proteins

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6
Q

Which of the following must encode RNA-dependent polyermase?
A. (+) SS RNA
B. (-) SS RNA

A

B. (-) SS RNA

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7
Q

_____: (+) sense RNA viruses that require DNA intermediate for replication (RNA to DNA to RNA)
A. Hep B Virus
B. Retrovirus
C. Hep C Virus

A

Retroviruses

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8
Q

_____: A gapped DNA genome; full-length but nicked (+) strand and partial (-) strand
A. Hep B Virus
B. Retrovirus
C. Hep C Virus

A

A. Hep B Virus

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9
Q

What are four mechanisms used to get many proteins out of small genomes?

A
  1. polyprotein synthesis
  2. leaky scanning
    - ribosomal binding sites
    - inefficient start codon
  3. reinitiation
    - many upstream ORF
  4. many ribosome binding sites
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10
Q

____: secondary structure that is important for efficient recognition of mRNA and translation

____: promotes packing of genome for assemebly into developing virions

A

IRES; packaging signals

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11
Q

True or False: Capsids can be Icosahedral or Helical

A

True

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12
Q

All humans with helical symmetry are ____

No DNA viruses have been discovered that are helical

A

enveloped

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13
Q

True or False: Enveloped viral envelopes take part of the plasma membrane with them, whereas non-enveloped leave cell without any host plasma membrane

A

True

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14
Q

Why are enveloped viruses wimpy?

A
  1. Envelopes break down fast outside of host
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15
Q

Which are harder to destroy: enveloped or non-enveloped viruses?

A

Non-enveloped – because they have stable capsid protein

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16
Q

____: Occurs after attachment; time between entry and production of new virus

____: Number of viruses undergoes exponential growth

A. Eclipse; Exponential
B. Exponential; Eclipse

A

A. Eclipse; Exponential

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17
Q

Three steps of viral infection?

A
  1. Attach, penetrate, and uncoat
  2. Transcription, translation, and replication
  3. Viral assembly, exit, and maturation
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18
Q

What are the three mechanisms for viral entry? Which is NOT pH dependent?

A

1) Uncoating at plasma membrane
- pH Independent
- No endosomal acidification

2) Uncoating within endosomes

3) Uncoating at nuclear membrane

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19
Q

A viral genome may or may not encode its own polymerase but no virus encodes its own ___ machinery. Thus, all viruses depend on host to make proteins

A

transcriptional

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20
Q

Which three places can viral assembly occur?

A
  1. Nucleus
    - Herpes
  2. Cytoplasm
    - Vacina
  3. Cell membrane
    - Retrovirus
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21
Q

How do non-enveloped viruses leave the cell?

How do enveloped viruses leave the cell?

A

Non-enveloped = Lysis

Enveloped = Budding

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22
Q

Which type of infection involves a non-permissive cell and a defective infecting virus? Ultimately, the host cell dies before virus is even made (no viral progeny made!)?

A. Persistent Infection
B. Abortive Infection
C. Latent Infection

A

B. Abortive Infection

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23
Q

Which type of infection allows viruses to constantly be made, with host cell maintaining normal function?

A. Persistent Infection
B. Abortive Infection
C. Latent Infection

A

A. Persistent Infection

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24
Q

True or False: In a latent infection, host cell survives and no virus is made, but some viral proteins are. Can be reactivated to make virus!

A

True

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25
Q

True or False: In oncogenic transformation, cells are immortalized

A

True

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26
Q

Abortive and Latent infections have ___ effect while___ infections cause senescence and cytolytic infections cause cell death

A

Abortive/Latent: no

Persistent: senescence

Cytolytic: cell death

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27
Q

What do you need to make a productive infection?

A
  1. Enough virus
  2. Permissive cells at infection site
  3. Absent local host defenses
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28
Q

Lymphatic spread is an example of ___ infection

A

systemic

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29
Q

How can viruses disseminate throughout body???

A

1) Lymphatics
2) Blood
3) Neurally

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30
Q

True or False: Virus must be grown in vitro

A

False - in cell culture

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31
Q

Three tests for detecting viruses?

A

1) Direct
- examined?

2) Indirect
- Specimen is incubated in presence of cells that allow for growth

3) Serology
- Ab titer against antigen

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32
Q

Electron/Light microscopy, Antigen detection, and molecular techniques are example of ___ virus examination

A

direct

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33
Q

Two steps to indirectly examining virus?

A

Step 1: cell culture
- primary cells (normal)
- semi-cont (embryonic)
- conti (immortal)

Step 2: presence of virus detected by
- tzanck smear
- cytopathic effect
- haemadsorption

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34
Q

True or False: Serology is used to diagnose a primary infection

A

True

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35
Q

Which two are acute infections?
A. HPV and HIV
B. HPV and Measles
C. Flu and Measles

A

C. Flu and Measles

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36
Q

True or False: HIV can either be a persistent/chronic infection or a slow, viral infection

A

True

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37
Q

True or False: HPV is a tumor related virus

A

True

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38
Q

Which two serotypes are important in influenza?
A. A and B
B. B and C
C. C and D

A

A. A and B

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39
Q

True or False: Orthomyxovirus can cause the flus - it is ENVELOPED, SEGMENTED, (-) ssRNA that is helical

A

True

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40
Q

Serotypes in influenza are based on M_ and M_

A

M1 (nucleocapsid protein)
M2 (membrane protein)

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41
Q

All three influenza viruses have both ___ (used to attach to human cells) and ___ peplomers

A

Hemagluttinin
- attach to human cells

Neuroaminidase
- penetration and release from infected human cells

42
Q

Which subtype of Influenza are based on antigenic variability of the envelop spikes?
A. Subtype A
B. Subtype B

A

A. Subtype A

43
Q

The influenza virus is capable of which two antigenic variation?

A

Antigenic drift
- point mutations in H/N glycoprotein genes
- A and B types

Antigenic shift
- major change due to genetic recombination of RNA segments
- new virus (change in hemagluttinin)
- only occurs in A !!!!
- could result in no herd immunity

44
Q

What are three ways that Influenza A virus gets antigenic variation?

A
  1. Mutation (shift/drift)
  2. Reassortment (shift)
  3. Recomb (shift)
45
Q

High fever is clinical manifestation of ___

A

flu

46
Q

Most common complication in influenza?

A

OM

47
Q

Two types of pneumonia that can arise from flu?

A

1 influenza pneumo
2 bacterial pneumonia

48
Q

How do you treat viral release in influenza?

A

NA inhibitor

49
Q

True or False: Both Oseltamivir and Zanamivir are NA inhibitors that treat Flu A and B

A

True

50
Q

Three types of flu vax?

A
  1. Killed - inactivate
    A. Eggs
    B. Multivalent
  2. Split-virus (subvirion)
  3. Live/Attenuated
    A. Nasal
51
Q

_____: acute, highly contagious disease characterized by fever, maculopapular rash, and post-infection sequlae.

Caused by: paramyxovirus (ssRNA)

A

Measles

52
Q

True or False: Humans are only host of measles

A

True

53
Q

Koplik spots during the prodromal phase and maculopapular rash (cytotoxic T cells) suggest ____

A

Measles

54
Q

True or False: OM is the most common complication of measles

A

True

55
Q

IgM via serology and lesions on oral mucus membrane suggests ___

A

measles

56
Q

MMRV is a vaccine against:

A

measles

57
Q

___ is an enveloped retrovirus, ss RNA genome that uses RT, Integrase, and Proteases
A. HPV
B. HIV
C. Measles

A

B. HIV

58
Q

____ and ____ are subsequently cleaved shortly after budding by HIV-1 protease into surface glyoproteins and mature Gag proteins, respectively
A. gp 160; Pr55Gag
B. Pr55Gag; gp 160

A

A. gp 160; Pr55Gag

59
Q

True or False: Humans are sole reservoir and host for HIV

A

True

60
Q

For viral entry of HIV into the cell HIV ___ binds to CD4, then undergoes conformational change that allows it to bind to two co-receptors (CCR5 and CXCR4)

Once gp120 binds to both CD4 and chemokine-R, gp41 undergoes conformational change

A

gp120

61
Q

During primary infection, what is the predominant HIV strain (uses CCR5 co-receptor)

A

M tropic HIV

62
Q

As HIV infection proceeds, there’s a switch in viral phenotype that gives rise to ____ HIV (uses CXCR4 co-receptor)
A. M tropic
B. T tropic

A

B. T tropic

63
Q

CCR5 is found on ____ R5 strains while CSCR4 is found on ____ X4 strains

A

M trophic; T trophic

64
Q

Koilocytotic cells suggest __

A

HPV

65
Q

In HPV, viral regulation of ___ is lost. Break occurs in ___ region.

A

E6/7; E2

66
Q

In HPV, when Tb is hyperphosphorylated (E2F) transcription is ____

A

repressed

67
Q

In HPV, L1 and L2 are the major and minor ___ proteins

E6 and 7 are ___ while E1 is a viral helicase that recruits DNAP

A

capsid

oncogenes

68
Q

True or False: In HPV, late genes make up the capsid while early genes are important for hijacking cellular functions

A

True

69
Q

True or False: CMI is required to control HPV

A

True

70
Q

Cervical papillomas and Condyloma acuminatum are associated with ___

A

HPV

71
Q

What is the most prevalent STD?

A

HPV

72
Q

In HPV, E6 binds to ___ while E7 binds to ___

A

E6 = p53
E7 = Rb

73
Q

Opthalmic zoster involves CN __

A

V

74
Q

Unilateral or vesicular rashes suggests ___

A

shingles

75
Q

Severe pain, burning, itching, rash (asymmetrical maculopapular or vesicular crusting that following a single thoracic dermatome/CN) suggests which condition?

A

Herpes zoster shingles

76
Q

Chickenpox is clinical manifestation of ___. Often associated with skin lesions on back and trunk, which can spread to the face.

A

Varicella

77
Q

True or False: In chickenpox, prodromal symptoms are often absent in the young

A

True

78
Q

VZV, an enveloped, dsDNA (thymidine kinase) can cause ____. It is neurotrophic, therefore can become latent.

A

chickenpox

79
Q

True or False: Chicken pox is a highly contagious, generalized lesions while Shingles is recrudescence of same virus

A

True

80
Q

Acyclovir can caused chain termination by acting on ____, not a cure however.

A

TK

81
Q

What can cause transition from HSV latency to virus production?

A

Increased in ICPO HSV gene expression, decreased in ICP4

82
Q

Which four factors promote transistion in HSV?

A
  1. Repression
  2. Sensory neurons
  3. LAT expression
  4. Inhibition of viral replication
83
Q

Which phase of HSV-1 active infection is associated with viral capsid assemble/progeny DNA encapsidation (nucleus). Virions then egress from the cell.
A. Phase 1
B. Phase 2
C. Phase 3
D. Phase 4

A

D. Phase 4

84
Q

Which phase of HSV-1 is associated with DNA replication, expression of late genes, and translation of late genes

A

Phase 3

85
Q

Which phase of HSV activation is associated with initiation of HSV genome replication?

A

Phase 2

86
Q

True or False: In Phase 2 of HSV-1 infection, early gene expression and IE protein transactivation is required for DNA replication

A

True

87
Q

In phase 1 of HSV-1 active infection, immediate early genes are expressed using __ ___ ___

A

Host RNA Polymerase

88
Q

What induces phase 2 of HSV-1 active infection?

A

IE RNA transcripts are translated. IE proteins induce stage 2!

89
Q

Which HSV gene is involved in DNA replication?

A

Early gene

90
Q

True or False: Late proteins are initiated after start of DNA synthesis in HSV

A

True

91
Q

Three hallmarks of latency?

A
  1. decreased gene expression
  2. reduced recognition by IS
  3. persistance of intact viral genome
  4. mechanism to re-enter productive phase of life cycle
92
Q

How do HAART drugs work against HIV?

A

Increase T cell count
Reduce vira load

Note: latent virus in T cells remain, despite therapy

93
Q

Integrase inhibitors can be use against which condition? How do they work?

A

HIV

  • decrease HIV viral repication when used in combo with HAART
94
Q

How do Fuzeon and Selzentry inhibit fusion and early entry in HIV?

A

Fuzeon = blocks gp41
Selzentry = blocks CCR5

95
Q

How do protease inhibitor work in HIV?

A

Block protease activity and viral maturation; binds irreversibly

96
Q

True or False: In HIV treatment, RTI cause viral DNA chain termination

A

True

97
Q

True or False: To treat HIV, NNRI’s block RT but do not incorporate into growing DNA chain

A

True

98
Q

Historically, HAART treatment for HIV has been 2 __ and a __

A

2 RTI + PI

99
Q

Analysis of presence of p24 suggests ___

A

HIV

100
Q

True or False: In HIV infection, neutralizing Ab are usually directed against gp120 while Cytotoxic T cells kill HIV infected cells, but also helper cells

A

True

101
Q

In HIV, low viral burden means __ disease progression while __ viral burden means ___ disease progression

A

slow
faster

102
Q

What are two mechanisms by which HIV reduces CD4+ T cells?

A

1) Direct
- Via CD4+ T cells

2) Indirect
- Autoimmune rx
- HIV specific CD8 T cells that kill helper cells

Medical Microbiology (31 decks)

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