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Microbiology 2110 > Viruses Exam 4 Microbiology > Flashcards

Viruses Exam 4 Microbiology Flashcards

1
Q

Virus

A

genetic element that can multiply only in a living (host) cell

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2
Q

Virus is latin for

A

poison

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3
Q

Viruses are

A

the most abundant biological entities on earth

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4
Q

Viruses infect what cells

A

bacteria, algae, fungi, protozoa, plants, and animals

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5
Q

Viruses needs

A

host cells for everything

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6
Q

Viruses have

A

their own nucleic acid genome

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7
Q

Virion

A

the infectious virus particle, the viral genome surrounded by a protein coat

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8
Q

The cause of viral infections are

A

Unknown

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9
Q

Louis Pasteur

A

hypothesized that rabies was caused by a living thing smaller than bacteria

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10
Q

They developed a vaccine for rabies in

A

1884

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11
Q

Dmitri Ivanovski and Martinus Beijernick showed that

A

a disease in tobacco (plant virus)

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12
Q

Loeffler and Frosch discovered

A

The animal virus causing foot and mouth disease in cattle

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13
Q

How did viruses originate

A

Progressive Hypothesis (genetic material capable of moving within a genome)
Escaped genes (Genetic fragments escaped from cells  developed protective coating  reenter cells to hijack machinery to reproduce )

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14
Q

Regressive Hypothesis aka Reductive evolution

A

Reduces the amount of gene that it carries in its genome… Adopts a parasitic lifestyle

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15
Q

Are viruses organisms, are they alive

A

They are nonliving and noncellular
Outside of the host cell they lack most features of life

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16
Q

What role did viruses play in the evolution of life

A

Shape the way cells, tissues, bacteria, plants, and animals have evolved

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17
Q

Human genome containing sequences that came from viruses

A

8%

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18
Q

Bacterial DNA containing viral sequences

A

10 to 20% od bacterial dna

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19
Q

Obligate intracellular parasites

A

Cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to make and release new viruses

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20
Q

Animal viruses were classified on the basis of

A

their hosts and the diseases they caused (Old System)

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21
Q

Newer classification systems emphasize the following

A

Hosts and disease they cause
Structure
Chemical composition
Similarities in genetic makeup

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22
Q

International Committee on the Taxonomy of Viruses:

A

8 orders and 38 families (another 84 families not yet assigned to any order)

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23
Q

Viruses are obligate intracellular parasites of

A

bacteria, protozoa, fungi, algae, plants, and animals

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24
Q

Viruses are

A

ubiquitous in nature and had major impact on development

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25
The size of viruses
Ultramicroscopic , ranging from 20nm up to 1000 nothin much diameter
26
Structure of viruses
Noncellular , very compact and economical
27
Nucleic acids can either be
Dna or Rna but not both
28
Molecules (Spikes)
are on the surface and gives them high specificity for attachment to the host cell
29
Viruses multiply by
taking control of host cell's genetic material
30
Which is NOT a potential origin method of viruses
Pre-life Hypothesis
31
How much of the human genome consists of viral sequences?
8%
32
Which of the following is False about viruses
They cannot infect algae
33
What component are viruses missing?
Ribosomes
34
Resemblance to cells
IT AINT NO RESEMBLANCE
35
Viral componet
External coating Core Containing nucleic acids (DNA or RNA) Matrix proteins and enzymes (occasionally)
36
Capsid
the protein shell that surrounds the genome of a virus
37
Naked
viruses have no other layers
38
Enveloped
viruses have an outer layer consisting of a phospholipid bilayer (from host cell membrane) and viral proteins
39
Nucleocapsid
nucleic acid + protein in enveloped viruses
40
Spikes
can be found on naked or enveloped viruse
41
Spikes allow
viruses to dock with host cells
42
Viral capsids
Most prominent feature of viruses
43
Capsomeres
identical protein subunits.. make up viral capsids
44
Capsomeres spontaneously
self assemble into the finished capsid
45
Two primary types of Capsids
Helical Icosahedral
46
Complex capsids
are never enveloped. only found in the viruses that infect bacteria
47
Enveloped viruses
Take a bit of the cell membrane when they are released from a host cell
48
Enveloped viruses can bud from
Cell membrane Nuclear envelope Endoplasmic reticulum
49
Viruses with a complex capsid infect what type of organism
Bacteria
50
The viral envelope is
more flexible than the capsid so enveloped viruses are pleomorphic
51
Genome
the sum total of the genetic information carried by an organism
52
Why do viruses have such a small amount of genes
Possess only the genes needed to invade host cells and redirect their activity
53
Escherichia coli has
4,000 genes
54
Humans have
21,000 genes
55
Having a larger genome allows...
cells to carry out the complex metabolic activity necessary for independent life.
56
Viruses typically posses
nly the genes needed to invade host cells
57
Double stranded
Linear or circular
58
RNA VIRUSES can be double stranded but
more often single-stranded
59
Positive-sense RNA:
ready for immediate translation
60
Negative-sense RNA:
must be converted before translation can occur
61
Segmented
individual genes exist on separate pieces of RNA  similar to human chromosomes
62
Retroviruses
carry their own enzymes to convert RNA -> DNA
63
Multiplication Cycles in Animal Viruses
Viruses are minute parasites that seize control of the synthetic and genetic machinery of cells
64
Length of replication
cycle varies from 8 hours in polioviruses to 36 hours in herpesviruses
65
Adsorption
A virus can invade its host cell only through making an exact fit with a specific host molecule
66
Host range of Adsorption
Hepatitis B: Liver cells of humans Poliovirus: Intestinal and nerve cells of primates Rabies: various cells of all mammals
67
Direct fusion of the viral envelope with the host cell membrane:
Envelope merges directly with the cell membrane
68
Penetration and Uncoating The flexible cell membrane of the host is
penetrated by the whole virus or its nucleic acid
69
Penetration through endocytosis
when a entire virus is engulfed by the cell and enclosed in a vacuole or vesicle
70
SYnthesis- DNA viruses
Enter the host cell’s nucleus and are replicated and assembled there
71
Synthesis- RNA Viruses
Replicated and assembled in the cytoplasm
72
Synthesis- Retroviruses turn their
RNA genomes into DNA
73
Assembly
virus is put together using “parts” manufactured during the synthesis process
74
Release
the number of viruses released by infected cells is variable, controlled by: Size of virus Health of the host cells
75
Virions released by infected cells vary
Poxvirus infected cell: 3,000 to 4,000 Provirus infected cells: 100,000 virions Immense Potential for rapid
76
Carrier relationships
cell harbors the virus and is not immediately lysed *Can remain latent in cytoplasm*
77
Provirus
Viral DNA incorporated into the DNA of the host E.g. Measles virus. HIV.
78
Chronic latent state:
Periodically become activated under the influence of various stimuli Ex. Herpes
79
Transformed cells
Increased rate of growth Changes in their chromosomes Changes in cell’s surface molecules Capacity to divide indefinitely
80
Oncoviruses: mammalian viruses capable of initiating tumors
Papillomaviruses Herpesviruses Hepatitis B virus
81
General phases of the animal viral replication cycle EXCEPT: Adhesion Penetration Uncoating Synthesis Assembly Release
Adhesion
82
During which phase of the animal viral replication cycle do we see nucleic acid replication and protein production
Synthesis
83
Bacteriophage "bacteria eating"
Contain double stranded DNA, some contain rna at times
84
Bacteriophage "bacteria eating"
Contain double stranded DNA, some contain rna at times
85
Bacteria that bacteriophages infect
More often pathogenic for humans
86
Every bacterial species is parasitized by...
various specific bacteriophages
87
T-even Bacteriophage
Most studied
88
T Even bacteriophage infects
Escherichia coli
89
Lysogeny
a condition in which the host chromosome carries bacteriophage DNA
90
Temperate phages do
Undergo absorption and penetration
91
Temperate phages do not
undergo replication or release
92
Viral DNA enters an inactive prophage state:
Inserted into bacterial chromosome -> Copied during normal bacterial cell division
93
Viral DNA enters an inactive prophage state:
Inserted into bacterial chromosome -> Copied during normal bacterial cell division
93
Viral DNA enters an inactive prophage state:
Inserted into bacterial chromosome -> Copied during normal bacterial cell division
94
Induction : Lysogeny
prophage in a lysogenic cell becomes activated and progresses directly into viral replication and the lytic cycle
95
The Role of Lysogeny in Human Disease
phage genes in the bacterial chromosome can cause the production of toxins or enzymes that the bacterium would not otherwise have
96
Lysogenic conversion
when a bacterium acquires a new trait from its temperate phage
97
corynebacterium diphtheriae - lysogenic temperate phage
diphtheria toxin
98
When phage nucleic acid is incorporated into the nucleic acid of its host cell and is replicated when the host DNA is replicated, this is considered part of which cycle?
lysogenic phase
99
A virus that undergoes lysogeny is a/an _________.
Temperate phage
100
Which of the following is incorrect about prophages?
Cause lysis of host cells

Microbiology 2110 (4 decks)

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