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BISC 303 > 17, 18. Viruses > Flashcards

17, 18. Viruses Flashcards

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1
Q

Latin meaning of virus?

A

Poison/toxin

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2
Q

3 main features of viruses?

A
  1. Simple acellular structure
  2. DNA or RNA (not both)
  3. Obligate intracellular parasites
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3
Q

Size of a virus?

A

10-400 nm (0.4 um)

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4
Q

of genes in a virus

A

Few to several hundred

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5
Q

2 examples of bacteria that are INTRACELLULAR PARASITES but have both DNA and RNA (and are therefore not viruses)?

A

Chlamydia

Rickettsia

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6
Q

3 structural elements of viruses?

A

Nucleocapsid core

DNA/RNA

Protein coat that binds nucleic acid

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7
Q

2 other special features of viruses?

A

Lipid membrane

Virally-encoded enzymes

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8
Q

Difference between virus and virion

A

Virus = replicative INTRAcellular form that infects cells

Virion = EXTRAcellular infectious particle that floats in the bloodstream and is NON-replicating

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9
Q

Viral capsid proteins are held together by what type of bond?

A

Non-covalent bonds

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10
Q

How many polypeptides are capsids comprised of?

A

One or a few

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11
Q

3 types of symmetry in capsids?

A

Helical, icosahedral, complex

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12
Q

Symmetry in Tobacco Mosaic Virus?

A

Helical

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13
Q

Example of a virus with icosahedral shape?

A

Adenovirus

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14
Q

What are naked viruses?

A

Viruses without lipid envelopes

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15
Q

2 things that influenza spike proteins encode?

A

Hemagglutinin

Neuraminidase

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16
Q

Function of hemagglutinin?

A

Crosslink and clump RBCs

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17
Q

What is neuraminidase?

A

Enzyme that clears host sialic acid to release virions upon budding

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18
Q

Virion = _______ + ________ +/- __________

A

Virion = nucleic acid + capsid +/- envelope

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19
Q

Genome sizes of viruses?

A

4000 - 500,000 nt

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20
Q

of proteins encoded by viral genome?

A

Few to 100+

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21
Q

2 ways viruses save space in the small genome?

A

Overlapping genes

No introns

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22
Q

2 types of RNA strands in RNA viruses?

A

”+” (sense)

”-“ (antisense)

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23
Q

What must -RNA (antisense) do before viral proteins can be translated?

A

Make a “+” (sense) strand complementary to the “-“ stand

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24
Q

Who discovered reverse transcriptase?

A

David Baltimore

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25
What is ICTV?
Internation committee for the taxonomy of viruses
26
The Baltimore system classification is based on what?
The nature of the viral genome and how the virus makes mRNA
27
How many groups of viruses are there based on the Baltimore system?
7
28
Retroviruses (like HIV) require what enzyme? Why?
Reverse transcriptase Copy +ssRNA to -DNA to make dsDNA
29
What are pocks?
Virally induced lesions
30
What are cytopathic effects?
Observable changes to cells due to viral replication Change depends on the virus and cell type used
31
In nature, plant viruses are often transmitted by ______
insects
32
What type of complex capsid structure do vaccinia virus have?
Pleiomorphic structure
33
Icosaghedral capsids are ___-sided polygon with ___ vertices
20-sided polygon 12 vertices
34
Helica capsid structure have ________ that form a helix which wrap around nucleic acids
Protomers
35
Who developed a porcelain filter that eliminated bacteria?
Chamberland
36
Iwanowski and Beijerinck discovered what?
Filtered extracts from tobacco could still transmit disease even after filtering through pores known to retain even the smallest bacteria Discovered the Tobacco mosaic virus
37
Who discovered bacteriophage?
Twort
38
Who created the bacteriophage plaque assay?
D'Herelle
39
Who discovered the sarcoma virus?
Peyton Rous
40
Chicken leukemia virus was discovered by..
Ellerman and Bang
41
Viruses recognize __________ because _______________________
host cells they bind to specific host cell receptors
42
What virus causes mononucleosis?
Epstein-Barr virus
43
Receptor (host) for Epstein-Barr virus?
Complement C3b receptor on B-lymphocytes
44
Receptor (host) for HIV?
CD4 on specific WBCs + co-receptor
45
Changes in what of either the virus/host cell receptor can influence the ability of the virus to infect?
molecular structure
46
2 common ways viruses enter host cells?
Membrane fusion Endocytosis
47
What are viral fusion proteins?
Specific virally encoded proteins that force envelope fusion w/ the plasma membrane
48
Naked virus entry via endocytosis - what enters the host cell cytosol?
ONLY the viral nucleic acid
49
What 2 factors are important for viral replication?
Specific viral receptors Cells that permit viral replication
50
What must occur in order for influenza to complete its viral life cycle?
Must infect the cell with ALL 8 segments of its genome
51
What is antigenic shift?
a LARGE change in the antigenic character of an organism that makes it unrecognized by the immune system
52
How many subtypes of hemagglutinin are there? Neuraminidase?
Hemagglutinin = 14 subtypes Neuraminidase = 9 subtypes
53
What does hemagglutinin bind to?
Host sialic acid (host cell receptor)
54
All _________ subtypes are present in birds
hemagglutinin
55
What Family does influenza belong to?
Orthomyxoviridae
56
Viral structure of influenza (nucleic acid, capsid shape, lipid envelope)?
(-)ssRNA Helical capsid Enveloped
57
What's unique about influenza's genome?
Segmented genome => 8 diff segments
58
Human rhinovirus receptor (host)?
VLDL receptor or ICAM-1
59
Example of a (-)ssRNA virus? What disease(s) does it cause?
Paramyxoviruses Mumps, measles
60
This family of viruses is known as "small RNA virus"
Picornaviruses
61
Example of a disease from picornaviruses?
Polio
62
Family of viruses that contain dsRNA?
Reoviruses
63
This virus goes through a DNA intermediate
HIV (human immunodeficiency virus)
64
What enzyme is required to replicate +, -, and +/- RNA viruses?
RNAP
65
3 sources of animal virus cultivation?
Suitable animal host Embryonic chicken eggs Cultured animal cells
66
2 sources of plant virus cultivation?
Whole plant Plant tissue culture
67
Different ______ create different plaque types
phages
68
Why are bacteriophage considered to have 'complex' symmetry?
Made up of a combination of capsid symmetries

BISC 303 (22 decks)

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