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Microbiology > Ch 13: Viruses, Viroids, and Prions > Flashcards

Ch 13: Viruses, Viroids, and Prions Flashcards

1
Q

What type of microscopy is needed to visualize viruses? How big are viruses?

A
  • Electron microscopy
  • 20-200 nm in size
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2
Q

Influenza viruses are classified by their ______

A

Hemagglutinin (HA) and Neuraminidase (NA) proteins

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3
Q

Is HIV a DNA or RNA virus?

A
  • RNA
  • Needs a DNA intermediate (reverse transcriptase)
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4
Q

What surface protein of HIV interacts with the CD4 receptor of T-cells?

A

gp120

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5
Q

What nucleic acid is inside an adenovirus?

A
  • Double-stranded DNA
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6
Q

What nucleic acid is inside a picornavirus?

A
  • Single-stranded (+)-RNA
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7
Q

What nucleic acid is inside a retrovirus?

A
  • 2 identical single-stranded (-)-RNAs
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8
Q

What nucleic acid is inside an orthomyxovirus?

A
  • 8 different single-stranded (-)-RNAs
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9
Q

What nucleic acid is inside a hepadnavirus?

A
  • “Gapped” dsDNA
  • DNA → RNA → DNA
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10
Q

Virus classifications by genome (I-VII)

A
  1. dsDNA (non-enveloped or enveloped)
  2. ssDNA (all non-enveloped)
  3. dsRNA (all non-enveloped)
  4. (+)-RNA (non-enveloped or enveloped)
  5. (-)-RNA (all enveloped; one or multiple RNAs)
  6. ssRNA → DNA
  7. dsDNA → ssRNA → dsDNA
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11
Q

What class of viruses are adenoviruses and papovaviruses?

A

Class I non-enveloped

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12
Q

What class of viruses are poxvirus and herpesvirus?

A

Class I enveloped

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13
Q

What class of viruses are parvoviruses?

A

Class II

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14
Q

What class of viruses are reoviruses?

A

Class III

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15
Q

What type of virus causes deadly diarrhea in children?

A

Reoviruses

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16
Q

What class of viruses are picornaviruses and caliciviruses?

A

Class IV non-enveloped

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17
Q

What class of viruses are togaviruses, flaviviruses, and coronaviruses?

A

Class IV enveloped

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18
Q

What class of viruses are rhabdoviruses, filoviruses, and paramyxoviruses?

A

Class V with one RNA molecule

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19
Q

What class of viruses are orthomyxoviruses, bunyaviruses, and arenaviruses?

A

Class V multiple RNAs

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20
Q

What class of viruses are retroviruses?

A

Class VI

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21
Q

What class of viruses are hepadnaviruses?

A

Class VII

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22
Q

What type of virus is hepatitis D?

A
  • It’s not a virus, it’s a virusoid
  • Piggybacks on hepatitis B
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23
Q

What types of viruses require reverse transcriptase? (Think about virus classes).

A
  1. Retroviruses
  2. Hepadnaviruses
24
Q

Circular dsDNA of a virus contains how many genes?

25
Q

How many base pairs are present in Theiler’s virus genome? (+)-RNA genome (one molecule)

A

7500 - 8000 bps

26
Q

How large is the genome of SARS-CoV-2?

27
Q

What family of viruses includes influenza?

A

Orthomyxoviruses

28
Q

Each segment of the influenza genome encodes for how many proteins?

A

one or two

29
Q

What receptors does HIV bind to?

A
  • CD4 (receptor)
  • CXCR4 (coreceptor)
30
Q

What is the target molecule of hemagglutinin (HA) in influenza?

A

Sialic acid (protein modification)

31
Q

What is the target molecule of the spike protein of SARS-CoV-2?

A

Angiotensin-Converting Enzyme 2 (ACE2)

32
Q

By what methods can an enveloped virus enter a cell? (2)

A
  1. Pinocytosis
  2. Fusion
33
Q

How do nonenveloped animal viruses enter a cell?

A

Genetic material is injected through the cell membrane similar to a bacteriophage

34
Q

If a virus needs to make DNA from DNA, it uses ____, unless ______

A
  • the host’s DNA-dependent DNA polymerase
  • unless it’s a cytoplasmic virus, then it uses its own
35
Q

If a virus needs to make RNA from DNA, it uses ______, unless it is _____.

A
  • Host’s RNA polymerase
  • Cytoplasmic
36
Q

If a virus needs to make RNA from (+)-RNA it ______

A
  • can encode its own polyerase
37
Q

If a virus needs to make RNA from (-)-RNA it ______

A

must bring its own polymerase

38
Q

If a virus needs to make DNA from RNA, it must ______

A

Bring in reverse transcriptase

39
Q

RNA viruses produce more variants per replication cycle than DNA viruses. Why?

A
  • DNA synthesis has low error rate because DNA polymerases can proofread
  • RNA synthesis has a high error rate because RNA polymerase cannot proofread (except for Coronaviruses)
40
Q

Why are viruses considered “quasispecies”?

A
  • There is no single “wild-type” virus
  • Have variants
41
Q

What is the function of Zidovudine (AZT)?

A
  • Inhibits reverse transcriptase
  • Acts as thymidine analog
  • Used as an antiretroviral to prevent and treat HIV/AIDS
42
Q

By what methods do viruses exit the host cell? (2)

A
  1. Lysis
  2. Budding
43
Q

What is obligate integration? What viruses utilize this?

A
  • Integration is required for the normal life cycle of a virus
  • Retroviruses
44
Q

What is conditional integration? What viruses utilize it?

A
  • Viruses that have special mechanisms that allow them to integrate at specific locations in the genome if the conditions are right
  • Certain bacteriophages
45
Q

What is rare integration? What viruses utilize it?

A
  • Some DNA viruses will on rare occasions integrate and cause disease
  • Herpesviruses and papovaviruses
46
Q

Where does HIV integrate into the genome?

A
  • Anywhere
  • Same with all retroviruses
47
Q

What is a prophage?

A

Bacterial DNA that has bacteriophage DNA integrated into it

48
Q

True or false. Animal viruses integrate at specific sites.

A

False. They typically integrate everywhere (a couple exceptions)

49
Q

What animal viruses do show integration into the host genome (to some extent)?

A
  1. Herpesviruses: integrate at low frequencies (Marek’s disease, Human Herpesvirus-6, Epstein-Barr)
  2. Papovaviruses: HPV can be found in cervical cancers
50
Q

In influenza, there are ___ subtypes of HA and ___ subtypes of NA.

51
Q

What is a host range?

A

Range of species a virus can infect

52
Q

What is tissue tropism?

A

THe types of different tissues an individual virus can infect

53
Q

Explain the tissue tropism of Measles?

A
  • First infects immune cells in lungs via SLAM receptor
  • Travels via these traveling cells to infect epithelial cells via Nectin 4 receptor
54
Q

What properties of influenza make it such a problem?

A
  1. Segmented RNA
  2. Broad host range

These properties allow new variants of viruses to emerge due to exchange of RNA segments inside the cell

55
Q

Why is a viroid not considered a true virus?

A
  • Lack a capsid
  • Infectious RNA that require viruses to spread them
  • Encode no proteins
  • Only in plants; except for Hepatitis D

Microbiology (19 decks)

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