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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
How many base pairs are present in Theiler's virus genome? (+)-RNA genome (one molecule)
7500 - 8000 bps
26
How large is the genome of SARS-CoV-2?
29,674
27
What family of viruses includes influenza?
Orthomyxoviruses
28
Each segment of the influenza genome encodes for how many proteins?
one or two
29
What receptors does HIV bind to?
* CD4 (receptor) * CXCR4 (coreceptor)
30
What is the target molecule of hemagglutinin (HA) in influenza?
Sialic acid (protein modification)
31
What is the target molecule of the spike protein of SARS-CoV-2?
Angiotensin-Converting Enzyme 2 (ACE2)
32
By what methods can an enveloped virus enter a cell? (2)
1. Pinocytosis 2. Fusion
33
How do nonenveloped animal viruses enter a cell?
Genetic material is injected through the cell membrane similar to a bacteriophage
34
If a virus needs to make DNA from DNA, it uses \_\_\_\_, unless \_\_\_\_\_\_
* the host's DNA-dependent DNA polymerase * unless it's a cytoplasmic virus, then it uses its own
35
If a virus needs to make RNA from DNA, it uses \_\_\_\_\_\_, unless it is \_\_\_\_\_.
* Host's RNA polymerase * Cytoplasmic
36
If a virus needs to make RNA from (+)-RNA it \_\_\_\_\_\_
* can encode its own polyerase
37
If a virus needs to make RNA from (-)-RNA it \_\_\_\_\_\_
must bring its own polymerase
38
If a virus needs to make DNA from RNA, it must \_\_\_\_\_\_
Bring in reverse transcriptase
39
RNA viruses produce more variants per replication cycle than DNA viruses. Why?
* 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
Why are viruses considered “quasispecies”?
* There is no single “wild-type” virus * Have variants
41
What is the function of Zidovudine (AZT)?
* Inhibits reverse transcriptase * Acts as thymidine analog * Used as an antiretroviral to prevent and treat HIV/AIDS
42
By what methods do viruses exit the host cell? (2)
1. Lysis 2. Budding
43
What is obligate integration? What viruses utilize this?
* Integration is required for the normal life cycle of a virus * Retroviruses
44
What is conditional integration? What viruses utilize it?
* Viruses that have special mechanisms that allow them to integrate at specific locations in the genome if the conditions are right * Certain bacteriophages
45
What is rare integration? What viruses utilize it?
* Some DNA viruses will on rare occasions integrate and cause disease * Herpesviruses and papovaviruses
46
Where does HIV integrate into the genome?
* Anywhere * Same with all retroviruses
47
What is a prophage?
Bacterial DNA that has bacteriophage DNA integrated into it
48
True or false. Animal viruses integrate at specific sites.
False. They typically integrate everywhere (a couple exceptions)
49
What animal viruses do show integration into the host genome (to some extent)?
1. Herpesviruses: integrate at low frequencies (Marek's disease, Human Herpesvirus-6, Epstein-Barr) 2. Papovaviruses: HPV can be found in cervical cancers
50
In influenza, there are ___ subtypes of HA and ___ subtypes of NA.
* 17 * 10
51
What is a host range?
Range of species a virus can infect
52
What is tissue tropism?
THe types of different tissues an individual virus can infect
53
Explain the tissue tropism of Measles?
* First infects immune cells in lungs via SLAM receptor * Travels via these traveling cells to infect epithelial cells via Nectin 4 receptor
54
What properties of influenza make it such a problem?
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
Why is a viroid not considered a true virus?
* 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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