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ch19 Flashcards

1
Q

Viruses can vary with respect to all of the following characteristics except __________.

A

the presence or absence of metabolic machinery

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2
Q

Which of the following is not a class I virus?

A

parvovirus

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3
Q

Prions are __________ that are thought to cause disease by __________.

A

abnormally shaped proteins; inducing similar but normally shaped proteins in the brain to adopt the abnormal form

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4
Q

Viral DNA incorporated into a bacterial chromosome is known as a(n) __________.

A

prophage

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4
Q

Some viruses have membranous envelopes. Where do viral envelopes typically originate from?

A

Membranes from the host cell

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5
Q

Restriction enzymes help defend bacteria against viral infections by __________.

A

cutting viral DNA once it has entered the cell

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6
Q

How does a retrovirus like HIV enter a host cell?

A

Glycoproteins on the viral envelope bind to receptors on the host cell. The viral envelope fuses with the host cell’s plasma membrane, facilitating uptake of the virus by the host cell.

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7
Q

Reverse transcription, carried out by retroviruses, is the process by which __________.

A

RNA information is copied into DNA

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8
Q

How do prions propagate and replicate themselves?

A

Prions convert normal proteins into the misfolded prion version.

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9
Q

Why are viruses often considered to be nonliving?

A

Viruses do not carry out metabolic processes, a primary characteristic of living organisms.

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10
Q

Which of the following is an example of vertical transmission of a virus in plants?

A

An infected plant produces seeds that contain the virus, giving rise to infected progeny.

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11
Q

Viruses that infect bacteria are called __________.

A

bacteriophages

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11
Q

When comparing DNA and RNA viruses, which mutate more quickly, and why?

A

RNA viruses, because no proofreading is done on RNA molecules

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11
Q

A widespread outbreak of a viral disease is called a(n) __________, and a global outbreak is called a(n) __________.

A

epidemic; pandemic

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12
Q

Candidates for the original source of viral genomes include __________.

A

plasmids and transposons

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13
Q

Circular RNA molecules that function like a virus in plants are termed __________.

A

viroids

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14
Q

Vaccines for viral diseases are __________ and help prevent infection by __________.

A

harmless derivatives of pathogenic viruses; stimulating the immune system to mount a defense against the actual pathogen

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15
Q

The avian flu virus H5N1 is considered a greater long-term threat than the swine flu virus H1N1 because __________.

A

it has a significantly higher mortality rate

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16
Q

When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?

A

Only the nucleic acid

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17
Q

HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because __________.

A

the virus binds to specific receptors that are only present on certain immune cells

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18
Q

Which of the following events occurs during the lytic life cycle of phages?

A

The host cell usually dies, releasing many new copies of the virus.

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19
Q

How are retroviruses different from other types of viruses?

A

Retroviruses use the enzyme reverse transcriptase to transcribe a copy of DNA from their own RNA.

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20
Q

A phage that inserts itself into the host DNA is called __________.

A

lysogenic

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21
Q

Which of the following statements correctly describes one difference between virulent phages and temperate phages?

A

Virulent phages replicate through the lytic cycle only, and temperate phages replicate using both the lytic and the lysogenic cycles.

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22
Why can flare-ups of herpes virus infection recur throughout a person's life?
Herpes virus can leave its DNA behind as minichromosomes in nerve cell nuclei. Stress can trigger another round of virus production, producing characteristic blisters and sores.
23
Class IV viruses are characterized by which of the following types of genomes?
single-stranded RNA that serves as mRNA
24
Animals that harbor and can transmit a particular virus but are generally unaffected by it are said to act as a __________ for that virus.
natural reservoir
25
The phage reproductive cycle that kills the bacterial host cell is a __________ cycle, and a phage that always reproduces this way is a __________ phage.
lytic; virulent
26
All of the following types of viruses have envelopes except __________.
picornovirus
27
How does a virus make more viruses?
Virus enters host cell and releases genome (DNA or RNA) - with some viruses, host cell bursts when the new viruses are released - with some viruses, the host cell remains alive after the new viruses are released
28
a virus consists of a nucleic acid surrounded by a
protein coat
29
virus
infectious particle consisting of genes packaged in a protein coat
30
viruses cannot
reproduce or carry out metabolism outside of a host cell
31
bacteriophages
viruses infect bacteria such as E. coli
31
viruses exist in a shady area between life-forms and chemicals, leading a
"borrowed life"
31
viruses are detected indirectly before
seen
32
viruses; not cells
very small infectious particle consisting; nucleic acid enclosed by protein coat and in some cases membranous envelope
32
viral genomes
dna virus; double or single stranded dna rna virus; double or single stranded rna
33
capsid
protein shell enclosing viral genome
33
capsomeres
protein subunit of capsids
34
a capsid is the protein shell that
encloses the viral genome
35
capsids are built from protein subunits called
capsomeres
36
membranous envelopes
assist in infection
37
viral envelopes
surround capsids of influenza and others found in animals
38
39
viruses obligate intracellular...
parasites, only replicate within host cell
40
host range
limited number of host cells can infect
41
inserted viral genome
cell manufactures viral proteins
42
viral nucleic acid molecules and capsomeres spontaneously
self-assemble into new viruses
43
bacteria defenses
restriction enzymes that recognize and cut up phage dna
44
once a viral genome has entered a cell...
the cell begins to manufacture viral proteins
45
virus makes use of
host enzymes, ribosomes, trnas, amino acids, atp, and other molecules
46
viral replicative cycle
1. entry and uncoating 2. replication 3. transcription and manufacture of capsid proteins 4. self assembly of new virus particles and their exit from the cell
47
lytic cycle
phage cycle with host cell death
48
virulent phage
phage only using lytic cycle
49
lysogenic cycle
phage genome replicates without destroying host
50
prophage
viral dna incorporated in hosts chromosome
51
lytic mode
environmental signal triggers virus genome to exit bacterial chromosome
52
temperate phages
phages using lytic and lysogenic cycles
53
lytic cycle of phage T4, a virulent phage
1. attachment 2. entry of phage dna and degradation of host dna 3. synthesis of viral genomes and proteins 4. self assembly 5. release
54
lysogenic cycle replicates
the phage genome without destroying the host
55
viral dna molecule is incorporated into the
host cells chromosome in the lysogenic cycle
56
phages that use both lytic and lysogenic cycles
temperate phages
57
lambda
temperate phage widely used in biological research
58
lytic cycle
- virulent or temperate phage - destruction of host dna - production of new phages - lysis of host cell causes release of progeny phages
59
lysogenic cycle
- temperate phage only -
60
viral glycoproteins (envelope) bind to
receptor molecules on host cell surface
61
viral envelopes
formed from host cells plasma membrane as capsids exit
62
retroviruses use
reverse transcriptase to copy their rna genome into dna
63
hiv
restrovirus that causes aids
64
provirus
viral dna integrated into host genome
65
unlike prophage...
provirus remains permanent resident of host cell
66
viruses
not living organism
67
viruses replicate only within
cells, evolved as bits of cellular nucleic acid
68
mimivirus
double stranded dna virus, largest virus and size of small bacterium
69
viral diseases
humans, agricultural crops, and livestock
70
viroids and prions
smaller, less complex entities cause disease in plants and animals
71
viruses
damage and kill cells - release of hydrolytic enzymes from lysosomes
72
infected cells produce toxins
disease symptoms
73
vaccines
harmless derivatives of pathogenic microbes that stimulate immune system to mount defenses against harmful pathogen
74
epidemic
widespread outbreak
75
1st cause of rapidly emerging viral diseases in humans
mutation of existing viruses into new ones that can spread more easily
76
2nd cause of rapidly emerging viral diseases in humans
spread of viral disease from a small isolated human population
77
3rd cause of rapidly emerging viral diseases in humans
spread of existing viruses from other animals - 3 quarters of new human diseases originate in this way
78
pandemic
global epidemic
79
influenza viruses
have 9 rna segments in their genome, leading to many new genetic combinations. - high rate of mutation
80
normal seasonal flu viruses are not considered emerging viruses because
variants of these viruses have been circulating among humans for a long time
81
seasonal flu viruses still undergo
mutation and reassortment
82
changes in host behavior or the environment can increase the spread of
viruses responsible for emerging diseases
83
new viral diseases can emerge when viruses spread from
animals to humans
84
viral diseases in small isolated population can
emerge and become global
85
viral strains that jump species can
exchange genetic information with other viruses to which humans have no immunity
86
horizontal transmission
entry in damaged cell walls
87
vertical transmission
inheriting virus from parent
88
viroids
small circular rna molecules that infect plants and disrupt their growth
89
prions
slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals - convert normal proteins into prions - mad cow disease
90
mosquitos
vector for a variety diseases between humans and animals. MOST DEADLY organism on the planet

Biology (18 decks)

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