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SYSTEMATICS > Viruses > Flashcards

Viruses Flashcards

1
Q

found he could transfer plant diseases by rubbing sap extract from diseased to healthy plants.
Conclusion: Disease is caused by small bacteria invisible under a microscope.

A

1883, Germany
Adolf Mayer

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2
Q

filtered sap from infected tobacco leaves, but sap still caused mosaic disease. o Conclusion: Bacteria small enough to pass thru filter caused the mosaic disease.

A

1890, Russia
Dimitri Ivanowsky

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3
Q

sap filtered thru bacterium-trapping filter. Filtered sap still caused the disease. Pathogen could replicate within the host.

Conclusion: The pathogen is not a bacterium but a replicating particle; generally credited for the concept of a virus.

A

1898, Netherlands
Martinus Beijernick

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4
Q

crystallized the infectious particle.

Confirmed the particle as the causative agent now called the Tobacco Mosaic Virus (TMV); viruses examined under EM. Viruses were detected long before they were seen.

A

1935, USA
Wendell Stanley

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5
Q

are not cells. They are particles. o Opportunist particles (alive when they attach to a living host)

A

Viruses

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6
Q

is a very small infectious particle consisting of nucleic acid (DNA or RNA) enclosed in a protein coat and, in some cases, a membranous envelope.

A

Viruses

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7
Q

The protein coat of a virus is called a

A

capsid

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8
Q

Capsids are built from protein subunits called

A

capsomeres

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9
Q

CAPSID STRUCTURES

A

Helical
Icosahedral
Membranous envelopes
Elongates icosahedral head with tail

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10
Q

CAPSID STRUCTURES
rigid rod-shaped capsid with a thousand molecules of single type protein arranged in a helix, as in TMV.

A

Helical

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11
Q

with 252 identical protein molecules arranged in a polyhedral shape with 20 triangular facets, e.g., Adenoviruses.

A

Icosahedral

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12
Q

derived from membranes of the host cell (with host’s phospholipids and membrane proteins + viral proteins and glycoproteins) e.g., influenza viruses.

A

Membranous envelopes

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13
Q

most complex; head encloses the DNA protein tail with fibers attaches to bacterial host; found in viruses that infect bacteria, bacteriophages or phages

A

Elongates icosahedral head with tail

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14
Q

Viral genomes may consist of either:

A

Double- or single-stranded DNA (dsDNA, ssDNA)

Double- or single-stranded RNA (dsRNA, ssRNA)

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15
Q

Depending on its type of nucleic acid, a virus is called a

A

DNA virus or an RNA virus.

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16
Q

The ______ of a virus is either a single linear or circular molecule of the nucleic acid.

A

genome

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17
Q

Viruses have between three and several thousand genes in their genome.

Bacteria contain 200 to a few thousand genes.

A

true

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18
Q

no envelope
double stranded dna
Respiratory viruses; tumor- causing viruses

A

Adenovirus

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19
Q

no envelope
double stranded dna
Warts, cervical cancer

A

Papillomavirus

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20
Q

no envelope
double stranded dna
Warts, cervical cancer tumors

A

Polyomavirus

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21
Q

single stranded rna serves as ____ to make a lot of copies of the virus

A

messenger rna

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22
Q

Single-Stranded RNA (ssRNA)
no envelope
Rhinovirus (common cold); po- liovirus; hepatitis A virus; other intestinal viruses

A

Picornavirus

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23
Q

envelope
Single-Stranded RNA (ssRNA)
Severe acute respiratory syndrome (SARS)

A

Coronavirus

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24
Q

envelope
Single-Stranded RNA (ssRNA)

Yellow fever virus; West Nile virus; hepatitis C virus

A

Flavivirus

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25
Q

envelope
Single-Stranded RNA (ssRNA)
Yellow fever virus; West Nile virus; hepatitis C virus

A

Togavirus

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26
Q

Serves as Template for mRNA Synthesis

A

ssRNA

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27
Q

ssRNA
envelope
Measles virus; mumps virus

A

Paramyxovirus

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28
Q

ssRNA
envelope
Human immunodeficiency virus (HIV/AIDS; see Figure 19.8); RNA tumor viruses (leukemia)

A

Retrovirus

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29
Q

Virus Taxonomy The ICTV has changed its Code (ICTV 2018) to allow a _____________ classification hierarchy that closely aligns with the Linnaean taxonomic system. This new structure can accommodate the entire spectrum of genetic divergence in the virosphere.

A

fifteen-rank

30
Q

Increase in transmissibility or detrimental change in virus epidemiology; or Increase in virulence or change in clinical disease presentation; or Decrease in effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics.

A

Variants of Concern

31
Q

is a pathogen’s or microorganism’s ability to cause damage to a host.

A

virulence

32
Q

compared to a reference isolate, its genome has mutations with established or suspected phenotypic implications, and has been identified to cause community transmission/ multiple cases/clusters, or has been detected in multiple countries.

A

Variants of Interest

33
Q

Viruses replicate only in

A

host cells

34
Q

Viruses are ________, which means they can replicate only within a host cell.

A

obligate intracellular parasites

35
Q

a limited number of host cells that it can infect, following a lock-and-key fit between the viral surface proteins and the receptor molecules of the host cell.

A

host range

36
Q

west Nile virus and equine encephalitis virus can each infect mosquitoes, birds, horses, humans are examples what range

A

Broad host ranges:

37
Q

virus can infect only humans, or one species, what range

A

Narrow host ranges:

38
Q

the viral DNA that is integrated into the host genome.

A

Prophage

39
Q

the viral DNA that is permanently integrated into the host genome.

A

Provirus

40
Q

are the best understood of all viruses

A

phages

41
Q

Phages have two reproductive mechanisms:

A

Lytic cycle
Lysogenic cycle

42
Q

is a phage replicative cycle that culminates in the death of the host cell

produces new phages and lyses (breaks open) the hosts cell wall, releasing the progeny viruses

A

LYTIC CYCLE

43
Q

A phage that reproduces only by the lytic cycle is called a

A

virulent phage

44
Q

__________ have defenses against phages, including restriction enzymes that recognize and cut up certain phage DNA

A

Bacteria

45
Q

replicates the phage genome without destroying the host.

The viral DNA molecule is incorporated into the host cell’s chromosomes.

Every time the host divides, it copies the phage DNA and passes the copies to daughter cells.

A

LYSOGENIC CYCLE

46
Q

This integrated viral DNA is known as a

A

prophage

47
Q

An ___l can trigger the virus genome to exit the bacterial chromosome and switch to the lytic mode

A

environmental signa

48
Q

Phages that use both the lytic and lysogenic cycles are called

A

temperate phages

49
Q

Viruses do not fit our definition of living organisms Since

A

viruses can replicate only within cells

50
Q

viruses are said to evolve from

A

bits of cellular nucleic acid

51
Q

Candidates for the source of viral genomes include:

A

Plasmids
Transposons

52
Q

small fragments of circular DNA.

A

Plasmids

53
Q

class of genetic elements that can “jump” to different locations within a genome. (=jumping genes).

A

Transposons

54
Q

Plasmids, transposons, and viruses are all mobile genetic elements.

A

true

55
Q

HOW DO VIRUSES CAUSE DISEASES IN ANIMALS?

A

Damage or kill cells by causing the release of hydrolytic enzymes from lysosomes.
* Cause infected cells to produce toxins that lead to disease symptoms.
Have molecular components such as envelope proteins that are toxic.

56
Q

TREATMENT AGAINST VIRUSES

A

Vaccines
Antiviral drugs
Defense frontline

57
Q

Viral infections cannot be treated by antibiotics.

A

true

58
Q

are harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the harmful pathogen.
can prevent certain viral illnesses.

A

Vaccines

59
Q

Antiviral drugs can help to treat, though not cure, viral infections.

A

true

60
Q

viruses that suddenly become apparent.

A

EMERGING VIRUSE

61
Q

are caused by new strains of influenza virus to which people have little immunity

A

Flu epidemics

62
Q

Viral diseases in small, isolated population can emerge and become global.

A

true

63
Q

New viral diseases can emerge when viruses spread from animals to humans .

Viral strains that jump species can exchange genetic information with other viruses to which humans have no immunity

A

(zoonotic)

64
Q

Most plant viruses have an RNA genome. Many have helical capsid, while others have an icosahedral capsid.

A

true

65
Q

Plant viruses spread disease in two major modes:

A

Horizontal transmission
Vertical transmission

66
Q

plant virus entering through damaged cell walls

A

Horizontal transmission

67
Q

plants inheriting the virus from a parent

A

Vertical transmission

68
Q

Smaller and simpler than viruses but as pathogenic as viruses.

A

VIROIDS AND PRIONS

69
Q

are circular RNA molecules that infect plant.

A

Viroids

70
Q

ex of viroids

A

Cadang-cadang caused deaths of 10 million coconut trees in the Philippines.

71
Q

are slow acting (10 yrs incubation) virtually indestructible infectious proteins that cause brain diseases in mammals.

propagate by converting normal proteins into the prion version

A

Prions

SYSTEMATICS (12 decks)

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