Abac Biol 3500 Chapter 9

Front 1

poison

Back 1

Virus means ___________ in latin.

Front 2

infectious

Back 2

A virus is an _________ particle

Front 3

Virion

Back 3

One virus particle is a _____________

Front 4

1. very small
2. contain very few genes
3. nucleic acids can be either DNA or RNA
4. Only grow within living cells

Back 4

Name 4 viral features which distinguish them from cells.

Front 5

20nm-300nm

Back 5

How small are viruses?

Front 6

4-200 genes

Back 6

How many genes does a virus have?

Front 7

1. ssDNA
2. dsDNA
3. ssRNA
4. dsRNA

Back 7

What are the 4 types of nucleic acid types found in viruses?

Front 8

obligate intracellular parasites

Back 8

A virus only grows within living cells so they are _______.

Front 9

host cell

Back 9

Viral proteins manufactured and nucleic acids replicated by the _______.

Front 10

False

Back 10

Viruses have ribosomes. (true/false)

Front 11

1. Make protein coat
2. Assure replication of own chromosome
3. Move in and out of cell

Back 11

What is the minimum genetic information in a virus?

Front 12

1. Polyhedral
2. Helical
3. Complex

Back 12

What are the three shapes of viruses?

Front 13

Polyhedral

Back 13

a virus having many flat surfaces

Front 14

Helical

Back 14

A viral shape in which capsomeres are spiraled around a core.

Front 15

Complex

Back 15

a combination of both helical and polyhedral shape.

Front 16

the shape of its protein coat (capsid)

Back 16

What determines the shape of the virus?

Front 17

Envelope

Back 17

What is the membrane that surrounds the capsid of some viruses?

Front 18

Host cell plasma membrane

Back 18

Where does the virus acquire an envelope?

Front 19

Budding

Back 19

What method of exit from the host cell results in an envelope?

Front 20

1. In the nucleus
2. the cytoplasm of the host cell

Back 20

Where do animal viruses replicate?

Front 21

adsorption

Back 21

The first step in infection is ______of the virus to the host cell.

Front 22

specific host cell receptors

Back 22

Where do viruses attach in the host?

Front 23

receptors

Back 23

The host cell is resistant if it lacks ________ to the virus.

Front 24

1. fusion
2. endocytosis

Back 24

What are the two methods of viral entry?

Front 25

envelopes

Back 25

Fusion occurs between the cytoplasmic membrane of the host with the virion ___________.

Front 26

endocytosis

Back 26

Both naked and enveloped virions enter by ________

Front 27

Uncoating

Back 27

The separation of the viral nucleic acid and the capsid is called ________.

Front 28

replication

Back 28

More viral nucleic acid is made by __________

Front 29

synthesis

Back 29

Capsid proteins are made by ___________.

Front 30

Maturation

Back 30

Self-assembly of viral component parts.

Front 31

1. Lysis of dead cells
2. Budding from living cells.

Back 31

What are the two methods of viral release from a host cell?

Front 32

1. dsDNA integrates into the host cell genome
2. dsDNA can replicate in host as a plasmid

Back 32

How does a dsDNA virus become part of the host cell genome?

Front 33

Temin, Baltimore and

Back 33

The scientists that discovered reverse transcriptase.

Front 34

Host cell makes a DNA copy of the viral RNA using reverse transcriptase which is then integrated into the chromosome of the host cell.

Back 34

How do RNA retroviruses become part of the host cell genome?

Front 35

reverse transcriptase

Back 35

What is the enzyme encoded by retroviruses that allows for the conversion of RNA to DNA?

Front 36

Defence mechanisms

Back 36

In the case of animals, outcome of infection depends on many factors independent of the infected cell such as the ______ of the host.

Front 37

Balanced pathogenicity

Back 37

The infection of an animal in which the microbe causes no obvious harm or disease.

Front 38

Prions

Back 38

Proteinaceous infectious particles

Front 39

transmissible spongiform encephalopathies

Back 39

Prions cause _____________

Front 40

Viriod

Back 40

Plant pathogens that are small ssRNA but no protein

Front 41

May be escaped introns

Back 41

Possible source of viriods.

Front 42

Complex Virus

Back 42

Virus morphology?

Front 43

Polyhedral (icosahedral) virus

Back 43

Virus morphology?

Front 44

Helical Virus

Back 44

Virus morphology?

Front 45

Scrapie

Back 45

Prion disesase seen in sheep and goats

Front 46

Kuru

Back 46

Prion disease seen in cannibals in New Guinea

Front 47

Bovine spongiform encephalopathy

Back 47

Mad cow disease

Front 48

1. Creutzfeldt-Jacob disease
2. Kuru
3. Gerstmann-Straussler syndrome
4. fatal familial insomnia
5. Variant CJD

Back 48

Name the prion diseases of humans

Front 49

PrPC

Back 49

The cellular prion protein

Front 50

PrPSc

Back 50

Scrapie protein

Front 51

Chronic Wasting Disease

Back 51

What is the prion disease of deer and elk?

Front 52

Kuru

Back 52

Which prion disease is also known as laughing disease?

Front 53

Transmissible mink encephalopathy

Back 53

What is the prion disease of Mink?

Front 54

Virus

Back 54

_____ is a genetic element that cannot replicate independently of a living (host) cell

Front 55

Virology

Back 55

____ is the study of viruses

Front 56

Viral infection

Back 56

A _______ occurs when a virus enters a host cell

Front 57

Conferring important properties.

Back 57

Not all viruses damage host cells. They may even be beneficial to the host by ______

Front 58

1.Either DNA or RNA genomes
2.Some circular, but most linear
3.single-stranded or double-stranded
4. one chromosome or segmented

Back 58

Describe viral genomes.

Front 59

bacteriophages

Back 59

Bacterial viruses are called ___________

Front 60

viridae

Back 60

Viral family names end in __________

Front 61

smaller

Back 61

Most viruses are ____ (smaller/larger) than prokaryotic cells

Front 62

smaller

Back 62

Most viral genomes ____ (smaller/larger) than those of cells

Front 63

Capsid

Back 63

________ is the protein shell that surrounds the genome of a virus particle

Front 64

Capsomere

Back 64

_____ is a subunit of the capsid

Front 65

Nucleocapsid

Back 65

________ is a complete complex of nucleic acid and protein packaged in the virion

Front 66

Helical

Back 66

Rod-shaped viruses have _______ symmetry

Front 67

length of nucleic acid

Back 67

Length of virus determined by________

Front 68

size and packaging of protein subunits

Back 68

Width of virus determined by _________

Front 69

Icosahedral

Back 69

Spherical viruses have ______ symmetry

Front 70

20

Back 70

Icosahedral viruses have _____ triangular faces

Front 71

Complex Viruses

Back 71

Virions composed of several parts, each with separate shapes and symmetries are _________

Front 72

Icosahedral heads and helical tails

Back 72

Describe a typical bacterial virus

Front 73

Enveloped

Back 73

A ____ virus contains additional membrane layers around the nucleocapsid

Front 74

embedded proteins

Back 74

The viral envelope is a lipid bilayer with______

Front 75

Enzymes for entry into host cell
Enzymes that are used to replicate genome
Enzymes to aid in release from the host cell

Back 75

What are the three types of enzymes critical to infection?

Front 76

Neuraminidase

Back 76

Enzymes that cleave glycosidic bonds

Front 77

Lysozyme

Back 77

Enzyme that makes hole in cell wall of bacteria

Front 78

Bacterial

Back 78

___ viruses are easiest to grow and are used as model systems

Front 79

Plant

Back 79

_____ viruses are typically most difficult to grow because study often requires growth of whole host

Front 80

Titer

Back 80

___ is the number of infectious units per volume of fluid

Front 81

Plaque assay

Back 81

____ are analogous to the counting bacterial colonies; one way to measure virus infectivity

Front 82

Plaques

Back 82

___ are clear zones that develop on lawns of host cells

Front 83

Lawn

Back 83

___ is a continuous (confluent) growth of bacterial or tissue culture

Front 84

a single virus particle

Back 84

Each plaque results from infection by _____

Front 85

Plaque-forming unit (PFU)

Back 85

____ is a measure of the number of virus particles capable of forming plaques per unit volume

Front 86

Infectious unit (IFU)

Back 86

____ is the smallest unit of virus that causes a detectable effect on a susceptible host

Front 87

Viral particles (VP)

Back 87

____ is the total number of viral particles, live and dead combined.

Front 88

lower

Back 88

The number of plaque-forming units is almost always ____ (lower/higher) than direct counts by electron microscopy

Front 89

Inactive virions
Incomplete virions
Conditions not appropriate for infectivity

Back 89

Why are plague-forming units lower than direct counts

Front 90

ID50

Back 90

The number of microbes to cause infection in 50% of test subjects.

Front 91

LD50

Back 91

The number of microbes to cause death in 50% of test subjects.

Front 92

1 Attachment
2 Penetration
3 Synthesis
4 Assembly
5 Release

Back 92

What are the phases of viral replication?

Front 93

Attachment

Back 93

____ is adsorption of the virus to a susceptible host cell

Front 94

Penetration

Back 94

______ is entry of the virion or its nucleic acid

Front 95

Synthesis

Back 95

_____ is the manufacturing of virus nucleic acid and protein by cell metabolism as redirected by virus

Front 96

Assembly

Back 96

____ is maturation of capsids and packaging of viral genomes into new virions

Front 97

Budding
lysis

Back 97

____ and ____ are the two methods of release of mature virions from the cell

Front 98

Endocytosis and fusion

Back 98

The two methods of entry of animal viruses into a host cell.

Front 99

Latent

Back 99

eclipse + maturation is the _____ period

Front 100

Enveloped

Back 100

Only _______ viruses can enter an animal cell by fusion.

Front 101

Eclipse

Back 101

____ is the period between adsorption of virus and the appearance of assembled virus progeny inside the cell

Front 102

Burst size

Back 102

______ is the number of virions released

Front 103

Class I

Back 103

Class ____ are double-stranded (ds) DNA viruses

Front 104

Class II

Back 104

Class ____ are single-stranded (ss) DNA viruses

Front 105

Class III

Back 105

Class ____ are dsRNA

Front 106

Class IV

Back 106

Class ____ are ssRNA +

Front 107

Class V

Back 107

Class ____ are ssRNA -

Front 108

Class VI
reverse transcriptase

Back 108

Class ____ ssRNA + retroviruses. Use _______ enzyme

Front 109

Class VII
reverse transcriptase

Back 109

Class ____ are dsDNA viruses that replicate through an RNA intermediate using _______ enzyme

Front 110

Attachment

Back 110

_____ requires complementary receptors on the surface of a susceptible host and its infecting virus

Front 111

carry out normal functions for cell (e.g., uptake proteins, cell to cell interaction)

Back 111

Receptors on host cell that the virus attaches to is used by the host to ________.

Front 112

penetration

Back 112

The attachment of a virus to its host cell results in changes to both virus and cell surface that facilitate ____.

Front 113

endocytosis

Back 113

Naked and enveloped viruses can enter by ____

Front 114

fusion

Back 114

Only enveloped viruses may enter by ______

Front 115

Uncoating

Back 115

___ is the process in which virions lose their outer coat and exposes the genome.

Front 116

Permissive cell

Back 116

____ is a host cell that allows the complete replication cycle of a virus to occur

Front 117

bacteriophage

Back 117

The type of virus that attaches to cells via tail fibers that interact with polysaccharides on the outer membrane of the host cell is a ____

Front 118

immune defense mechanisms
RNA interference

Back 118

What are the eukaryotes mechanisms to diminish viral infections?

Front 119

CRISPR- Similar to RNA interference Restriction modification system

Back 119

What are the prokaryotes mechanisms to diminish viral infections?

Front 120

double-stranded DNA

Back 120

DNA destruction system of bacteria are only effective against _____viruses

Front 121

Restriction enzymes (restriction endonucleases)

Back 121

____ cleave DNA at specific sequences

Front 122

Chemical modification of viral DNA (glycosylation or methylation)
Production of proteins that inhibit host cell restriction system

Back 122

How does a virus evade bacterial restriction systems?

Front 123

Baltimore

Back 123

____developed classification scheme for viruses based on relationship of viral genome to its mRNA

Front 124

retroviruses
reverse transcriptase

Back 124

Baltimore, Temin, and Dulbecco discovered ____ and _____

Front 125

plus (+)

Back 125

mRNA is said to be in ____ configuration

Front 126

genome
proteins

Back 126

Once a host has been infected, new copies of the viral _____ must be made and virus-specific ____ synthesized in order for the virus to replicate

Front 127

Positive

Back 127

____strand RNA virus: single-stranded RNA genome with same orientation as its mRNA

Front 128

Negative

Back 128

____ strand RNA virus: single-stranded RNA genome with orientation complementary to its mRNA

Front 129

1 synthesized soon after infection
2 necessary for replication of virus nucleic acid
3 typically act catalytically
4 synthesized in smaller amounts

Back 129

What are the characteristics of early proteins?

Front 130

1 Synthesized later Include proteins of virus coat
2 Typically structural components
3 Synthesized in larger amounts

Back 130

What are the characteristics of late proteins?

Front 131

dsDNA

Back 131

Most phages contain ____ genomes

Front 132

lytic

Back 132

Temperate phages can also be ____

Front 133

Early and middle proteins

Back 133

____ are enzymes needed for replication and transcription

Front 134

Late proteins

Back 134

_____ are head and tail proteins and enzymes required to liberate mature phage particles

Front 135

Lysogenic

Back 135

Temperate viruses can undergo a stable genetic relationship within the host. This is the _____ pathway

Front 136

Lysogeny

Back 136

____ is a state where most virus genes are not expressed and virus genome (prophage) is replicated in synchrony with host chromosome

Front 137

Lysogen

Back 137

___ is a bacterium containing a prophage

Front 138

lytic

Back 138

Viruses can enter a virulent mode in which it kills cells through____ pathway

Front 139

lytic

Back 139

Under certain conditions lysogenic viruses may revert to the ____ pathway and begin to produce virions

Front 140

Budding

Back 140

____ occurs as animal viruses leave host cell, they can remove part of host cell’s lipid bilayer for their envelope.

Front 141

Persistent

Back 141

During ____ infections, release of virions from host cell does not result in cell lysis

Front 142

Latent

Back 142

During ____ infections, there is a delay between infection by the virus and lytic events

Front 143

Transformation

Back 143

____ is the conversion of normal cell into tumor cell

Front 144

Cell fusion

Back 144

___ occurs when two or more cells become one cell with many nuclei

Front 145

Retroviruses

Back 145

____ are RNA viruses that replicate through a DNA intermediate

Front 146

two identical ssRNA molecules of the plus (+) orientation

Back 146

Retroviruses have a unique genome which consists of __________

Front 147

1.Entrance into the cell
2.Removal of virion envelope at the membrane
3.Reverse transcription of one of the two RNA genomes
4.Integration of retroviral DNA into host genome
5.Transcription of retroviral DNA
6.Assembly and packaging of genomic RNA
7.Budding of enveloped virions; release from cell

Back 147

What is the process of replication of a retrovirus?

Front 148

Defective

Back 148

_____ viruses that are parasitic on other viruses

Front 149

Defective

Back 149

_____ viruses require other virus (helper virus) to provide some function

Front 150

Satellite

Back 150

_______ viruses are defective viruses for which no intact version exists; rely on unrelated viruses as helpers

Front 151

Viroids

Back 151

____ are infectious RNA molecules that lack a protein coat

Front 152

plant

Back 152

Viriods cause a number of important ____ diseases

Front 153

Small, circular, ssRNA molecules

Back 153

Describe the genome of viriods.

Front 154

Prions

Back 154

____ are infectious proteins whose extracellular form contains no nucleic acid

Front 155

transmissible spongiform encephalopathies

Back 155

Prions cause disease in animals called ______

Front 156

PrnP

Back 156

Host nerve cell contains gene ___ that encodes native form (PrPc) of prion protein that is found in healthy animals

Front 157

PrPc

Back 157

The native form of prion protein that is found in healthy animals is ______

Front 158

PrPSc

Back 158

_____results form prion misfolding and causes neurological symptoms of disease (e.g., resistance to proteases, insolubility, and aggregation)

Front 159

1.Infectious prion disease
2.Sporadic prion disease
3.Inherited prion disease

Back 159

What are the three distinct mechanisms of prion diseases?

Front 160

Infectious

Back 160

During _____ prion disease, a pathogenic form of prion protein is transmitted between animals or humans

Front 161

Sporadic

Back 161

During _____prion disease, random misfolding of a normal, healthy prion protein in an uninfected individual

Front 162

Inherited

Back 162

During _____ prion disease, a mutation in prion gene yields a protein that changes more often into disease-causing form

Front 163

Virulent

Back 163

During the _____ mode, viruses lyse host cells after infection

Front 164

Temperate

Back 164

During the ______mode, viruses replicate their genomes in tandem with host genome and without killing host