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BISC 303 > 17, 18. Viruses > Flashcards

17, 18. Viruses Flashcards

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
Q

What is ICTV?

A

Internation committee for the taxonomy of viruses

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26
Q

The Baltimore system classification is based on what?

A

The nature of the viral genome and how the virus makes mRNA

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27
Q

How many groups of viruses are there based on the Baltimore system?

A

7

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28
Q

Retroviruses (like HIV) require what enzyme? Why?

A

Reverse transcriptase

Copy +ssRNA to -DNA to make dsDNA

29
Q

What are pocks?

A

Virally induced lesions

30
Q

What are cytopathic effects?

A

Observable changes to cells due to viral replication

Change depends on the virus and cell type used

31
Q

In nature, plant viruses are often transmitted by ______

A

insects

32
Q

What type of complex capsid structure do vaccinia virus have?

A

Pleiomorphic structure

33
Q

Icosaghedral capsids are ___-sided polygon with ___ vertices

A

20-sided polygon

12 vertices

34
Q

Helica capsid structure have ________ that form a helix which wrap around nucleic acids

A

Protomers

35
Q

Who developed a porcelain filter that eliminated bacteria?

A

Chamberland

36
Q

Iwanowski and Beijerinck discovered what?

A

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
Q

Who discovered bacteriophage?

A

Twort

38
Q

Who created the bacteriophage plaque assay?

A

D’Herelle

39
Q

Who discovered the sarcoma virus?

A

Peyton Rous

40
Q

Chicken leukemia virus was discovered by..

A

Ellerman and Bang

41
Q

Viruses recognize __________ because _______________________

A

host cells

they bind to specific host cell receptors

42
Q

What virus causes mononucleosis?

A

Epstein-Barr virus

43
Q

Receptor (host) for Epstein-Barr virus?

A

Complement C3b receptor on B-lymphocytes

44
Q

Receptor (host) for HIV?

A

CD4 on specific WBCs + co-receptor

45
Q

Changes in what of either the virus/host cell receptor can influence the ability of the virus to infect?

A

molecular structure

46
Q

2 common ways viruses enter host cells?

A

Membrane fusion

Endocytosis

47
Q

What are viral fusion proteins?

A

Specific virally encoded proteins that force envelope fusion w/ the plasma membrane

48
Q

Naked virus entry via endocytosis - what enters the host cell cytosol?

A

ONLY the viral nucleic acid

49
Q

What 2 factors are important for viral replication?

A

Specific viral receptors

Cells that permit viral replication

50
Q

What must occur in order for influenza to complete its viral life cycle?

A

Must infect the cell with ALL 8 segments of its genome

51
Q

What is antigenic shift?

A

a LARGE change in the antigenic character of an organism that makes it unrecognized by the immune system

52
Q

How many subtypes of hemagglutinin are there? Neuraminidase?

A

Hemagglutinin = 14 subtypes

Neuraminidase = 9 subtypes

53
Q

What does hemagglutinin bind to?

A

Host sialic acid (host cell receptor)

54
Q

All _________ subtypes are present in birds

A

hemagglutinin

55
Q

What Family does influenza belong to?

A

Orthomyxoviridae

56
Q

Viral structure of influenza (nucleic acid, capsid shape, lipid envelope)?

A

(-)ssRNA

Helical capsid

Enveloped

57
Q

What’s unique about influenza’s genome?

A

Segmented genome => 8 diff segments

58
Q

Human rhinovirus receptor (host)?

A

VLDL receptor or ICAM-1

59
Q

Example of a (-)ssRNA virus? What disease(s) does it cause?

A

Paramyxoviruses

Mumps, measles

60
Q

This family of viruses is known as “small RNA virus”

A

Picornaviruses

61
Q

Example of a disease from picornaviruses?

A

Polio

62
Q

Family of viruses that contain dsRNA?

A

Reoviruses

63
Q

This virus goes through a DNA intermediate

A

HIV (human immunodeficiency virus)

64
Q

What enzyme is required to replicate +, -, and +/- RNA viruses?

A

RNAP

65
Q

3 sources of animal virus cultivation?

A

Suitable animal host

Embryonic chicken eggs

Cultured animal cells

66
Q

2 sources of plant virus cultivation?

A

Whole plant

Plant tissue culture

67
Q

Different ______ create different plaque types

A

phages

68
Q

Why are bacteriophage considered to have ‘complex’ symmetry?

A

Made up of a combination of capsid symmetries

BISC 303 (22 decks)

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