Chapter 6

Identify all the methods that a virus can use to gain entry into an animal cell.

-Fusion of the viral envelope and the cell membrane -Engulfment/phagocytosis of the virus

Identify any benefits of viruses to people.

-Some viruses control food pathogens -Some viruses can be modified to deliver genetic cures via gene therapy -Some viruses control insect pests

Which facts best support the position that viruses are not living organisms?

-Viruses do not have any means of independent metabolism. -Viruses cannot reproduce on their own.

List the correct order of viral life cycle phases, starting with the first at the top.

-adsorption -penetration/uncoating -synthesis -assembly -release

Two shapes of viral capsids are _______ , which resembles a bracelet; or _______ , which is a type of polyhedron.

-helical -icosahedral

Which suffix represents a viral family?

-viridae

Which suffix represents a viral genus?

-virus

Select the infectious agents that are noncellular.

1) Prions 2) Satellite viruses 3) Viroids

Order the following steps to reflect the order in which they occur in the life cycle of an animal virus.

1. Adsorption (attachment) to host cell surface 2. Penetration and uncoating 3. Synthesis of viral nucleic acid and proteins 4. Assembly of viral particle 5. Release from host cell

Order the following choices in terms of size, from smallest to largest.

1. Viruses 2. Bacteria 3. Protozoa 4. Helminths

What is the correct order of the stages for phage replication? 1 = assembly 2 = attachment 3 = transcription/replication 4 = release 5 = penetration

2, 5, 3, 1, 4

During replication of the positive (+) sense strand of lytic RNA phage, in order to make more positive (+) strands, _______.

All of the choices are correct

Identify any of the following which can be used as primary cell lines.

Any of the answers listed here

Which of the following describes the various viral parts coming together to produce virions?

Assembly

During the _____ step in the viral multiplication cycle, capsids and genetic material are packaged into virions. Please give the specific term for this step.

Assembly (viral)

Which of the following viral release methods will not initially destroy the cell?

Budding

Different viruses can infect which of the following?

Human, bacterial, or plant cells

______ bodies are masses of viruses or damaged organelles of a cell due to a cytopathic effect of viral infection.

Inclusion

Which of the following is a mass of viruses or damaged organelles due to the cytopathic effect of viral infection?

Inclusion body

When an RNA viral genome is described as segmented, this means that ______.

Individual genes are fragmented into small pieces of RNA

At minimum, all viruses are composed of

nucleic acids and proteins

Viruses that are ______ lead to cancer in infected hosts.

oncogenic

In the penetration step of phage replication, _______.

only the phage nucleic acid enters the bacterial cell

A major difference in the replication of animal viruses and bacteriophages is the ______ step.

penetration

A(n) ________ is observed as a clear area where phage-infected bacterial cells cultivated on agar have been disrupted.

plaque

One way to detect the growth of a virus in culture is to observe the degeneration and lysis of infected cells in the monolayer of cells. These areas are:

plaques

A(n) _____ is a proteinaceous infectious agent associated with spongiform encephalopathies.

prion

Bacteriophages can infect which of the following?

prokaryotes only

Phage DNA that is latently incorporated into the bacterial host genome is called a ____.

prophage

At minimum, viruses are composed of nucleic acid covered by a coating comprised of ________

protein

Capsomeres are composed of _______ .

protein

Viral capsids are composed of _____.

protein

In the attachment step of phage replication, _______.

protein fibers in the phage tail attach to specific receptors on the bacterial cell wall

The capsid of a virus is _______.

protein shell that surrounds the nucleic acid

Which of the following best describes a prion?

proteinaceous infectious agent

Which macromolecule composes capsomeres?

proteins

A _______ is the stage of an animal virus life cycle which is integrated into the host cell's genome.

provirus

The host cells that viruses can infect are determined by the _______.

receptors on the host cells

Phage DNA encodes for the proteins of the viral capsid and _______.

regulatory proteins which direct the production and assembly of the capsid proteins

When it comes to virus multiplication, viral exocytosis refers to ______.

release

What are viruses called which are capable of converting their RNA genomes into DNA?

retroviruses

An enzyme capable of taking an RNA genome and generating a DNA copy is called ______.

reverse transcriptase

In some viruses, including HIV, the enzyme ______ _______ transcribes RNA into DNA.

reverse transcriptase

The enzyme ______ _____ is a preformed protein carried in by HIV responsible for converting its RNA genome into DNA.

reverse transcriptase

A noncellular infectious form that depends on other viruses for replication is known as a(n) _______ virus.

satellite

When an enveloped virus buds off the cell membrane, the membrane differs ______ from the host cell's membrane.

significantly

Viral glycoproteins that protrude from the viral envelope and attach to host cell receptors are termed _____.

spikes

A _______ occurs when a virus induces multiple cells to fuse making a large multinucleated cell.

syncytium

What was the significance of the discovery of filterable viruses?

It demonstrated that infections could be caused by agents that were smaller than bacteria.

How does bacteriophage DNA get into the host cell?

It is injected

The ______ refers to the capsid and nucleic acid of a nonenveloped virus.

Nucleocapsid

Select all of the terms that can be accurately used to describe a virus.

Obligate intracellular parasite Infectious particle

Which of the following best describe the relationship between viruses and their host cell?

Parasitism

Which of the following describes the "clear" area where a phage-infected cell lysed and infected all the neighboring cells and lysed those too.

Plaque

Which of the following is used to describe the phage DNA that is latently incorporated into the bacterial host genome?

Prophage

Which of the following describe an animal virus that has integrated its genome into the host cell's genome?

Provirus

An envelope is acquired during which step of the viral life cycle?

Release

HIV is described as a(n) _______ because it synthesizes DNA from RNA using reverse transcription.

Retrovirus

Which of the following is an enzyme found in HIV that is responsible for converting its RNA genome into a DNA genome?

Reverse transcriptase

Which of the following denotes the family name of the rabies virus?

Rudiviridae

What term is used to describe a virus type which depends on other viruses for replication?

Satellite virus

Which term describes the integration of an oncogenic virus that changes mammalian host DNA?

Transformation

A positive-sense RNA genome is ready for immediate ______.

Translation to protein

A portion of the viral envelope comes from the cell membrane of the host cell.

True

T or F: Almost immediately upon entry, the viral nucleic acid alters the genetic expression of the host cell.

True

T or F: Phage lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.

True

T or F: Phage-induced lysozyme lyses the host cell releasing the newly made phage.

True

True or false: Budding viruses do not lyse the host cell during release.

True

True or false: Embryonic tissue can serve as a primary cell line for viral culture.

True

True or false: Inoculation of laboratory animals is an in vivo method of viral cultivation.

True

True or false: Mad cow disease can be transmitted to humans through consumption of infected beef.

True

True or false: Viral nucleic acid may be single-stranded or double-stranded DNA or RNA.

True

True or false: Viruses are among the smallest infective agents.

True

True or false: Viruses can be both harmful or beneficial to humans.

True

True or false: Viruses can contain either DNA or RNA, but not both.

True

A fully formed virus that is able to establish an infection in a host cell is often called a ______.

Virion

Which of the following statements regarding the membrane on an enveloped virus is true?

Viruses insert their own proteins in the membrane.

What does "obligate" mean in regard to viruses?

Viruses must have a host cell

A(n) ______ is an infectious agent that lacks a capsid and merely consists of a strand of RNA.

Vivoid

Which viral stage occurs first?

adsorption

The general steps in a viral multiplication cycle are ________.

adsorption, penetration, synthesis, assembly, and release

The general steps in viral replication (in order) are _______.

adsorption, penetration, synthesis, assembly, release

Identify the proper order of phases in the life cycle of animal viruses:

adsorption, penetration, uncoating, synthesis, assembly, and release.

Spikes are essential for the

attachment of the viruses to the host cell

Any virus that specifically infects bacteria is called a(n)

bacteriophage

In the release process, the viral capsid _______.

becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded

Two ways in which newly assembled viruses are released from host cells are through ____________ (exocytosis) by enveloped viruses, and through ___________ (rupture) by naked viruses.

budding lysis

Enveloped viruses are usually released from the host cell by _______.

budding/exocytosis

A positive (+) strand of RNA _______.

can directly act as mRNA

Some host cells can harbor a virus and not be immediately lysed by the virus. This results in a persistent infection and is known as a(n)

carrier relationship

When referring to a microbe that cannot reproduce, the term ______ is to bacteria as the term ______ is to viruses.

dead; inactive

Every virus particle contains _____.

either DNA or RNA

The 2 principle processes by which viruses penetrate host cells are ________ (engulfment) and direct fusion.

endocytosis

Which term is used to describe the process when a virus is engulfed by a cell in a vacuole or vesicle?

endocytosis

Which term is used to describe the phospholipid bilayer found surrounding the capsid of some viruses?

envelope

A(n) _____ virus has a membranous layer external to the nucleocapsid.

enveloped

Budding is a type of ______ process where enveloped viruses are released from the host cell membrane.

exocytic

All viruses leave a cell by exocytosis. T/F

false

T or F: Animal viruses always kill cells they infect.

false

T or F: C. diphtheriae produces a toxin that is really encoded by a lytic phage infecting this bacterium.

false

T or F: T-even phages can replicate independently of a host cell.

false

T or F: There are many more antiviral drugs available on the market to treat viral infections than the number of antibiotic drugs available to treat bacterial infections today.

false

T or F: Viruses can be grown on culture media like bacteria.

false

True or false: Viruses which can lead to cancer are termed carcinoviruses.

false

The membrane receptors that viruses attach to during adsorption are typically composed of ______.

glycoproteins

What are the viral spikes typically composed of?

glycoproteins

Viruses which have a series of rod-shaped capsomer proteins linked together forming a series of interconnected hollow discs are termed ______.

helical

Viral transformation implies ______.

host DNA is changed

If the term "dead" is used to describe a particular bacterial cell then the term _____ would be used to describe a virus in a similar condition.

inactive

Identify the viral disease from the list below.

influenza

Lysogeny is best described as ______.

integration of the viral genome into the host chromosome

The term _______ is used to describe how some viruses burst cells during the release stage of viral multiplication.

lysis

Viral cycles that end in release of the new phages and immediate destruction of the host bacterial cell are referred to as ______.

lytic

The disease bovine spongiform encephalopathy is also known as

mad cow disease

A _______ virus does not have an envelope surrounding its capsid.

naked

A nonenveloped virus is also called a(n) ______ virus.

naked

In _____ -sense RNA viral genomes, the RNA is not in a form ready for translation.

negative

In ______ -sense RNA viral genomes, the RNA is not in a form ready for translation.

negative

The central core of a virus particle consists of

nucleic acid

Identify all the components of the nucleocapsid.

nucleic acid and capsid

In which way do enveloped viruses leave their host cell?

Budding

Identify prion related diseases.

-Bovine spongiform encephalopathy -Creutzfeldt-Jakob disease

Identify which of the following statements represent activities that viruses CANNOT do.

-Consume food -Replicate outside of a cell

Identify the different environments in which some viruses can replicate.

Bacterial, human, and animal cells

What term is used to specifically describe the types of viruses that infect bacteria?

Bacteriophage

Which is closest in physical proximity to the nucleic acid of a virus?

Capsid

Which are the three main criteria used in classifying viruses into families?

Chemical composition Structure Genetic makeup

Viruses ______ depend on a host cell for replication

Completely

Which is the typical route of infection for mad cow disease?

Consumption of contaminated food

Which prion-associated spongiform encephalopathy is marked by dementia, impaired senses, and uncontrolled muscle contractions?

Creutzfeldt-Jakob disease

A single virion could contain a genome of

DNA only RNA only

Viral nucleic acids are ______.

Either single-stranded or double stranded

Which of these terms does not belong in this group?

Embryonic culture

The process of _______ , a type of penetration, occurs when viruses are taken into the cell followed by engulfment in a vacuole or vesicle.

Endocytosis

The T-even bacteriophages such as T2 and T4 infect _______.

Escherichia coli

T or F: A positive sense strand lytic RNA phage attaches to the cell wall of an E. coli bacterium.

False

T or F: Once a phage becomes lysogenic, it will remain lysogenic and never be lytic again.

False

True or false: Bacteriophages infect eukaryotic and prokaryotic microorganisms.

False

True or false: The viral envelope and capsid are the same thing.

False

Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside.

False

Who postulated the idea that there are "living things" smaller than bacteria and proposed the term "virus"?

Louis Pasteur

The term ______ is used to describe how some viruses burst cells during the release stage of viral multiplication.

Lysis

Which term correctly refers to viral bursting of any host cell?

Lysis

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 cycle

Which term refers to the persistence of bacteriophages within host cells?

Lysogeny

Which of the following denotes the genus of rabies virus?

Lyssavirus

When present, what is the viral envelope composed of?

Mainly lipids

Which of the following terms is used to describe a viral RNA genome which CANNOT be immediately translated into protein?

Negative-sense

What term is used to describe the viral proteins which protrude from the envelope and aid in attachment to host receptors?

Spikes

Viruses are classified into families based on genetic makeup, chemical composition, and ______.

Structure

Which of the following is a multinucleated mass of cells due to the cytopathic effect of viral infection?

Syncytium

Cell culture and ______ culture have the same meaning.

tissue

Select the three choices that represent the primary purposes of cultivating viruses.

to isolate viruses from clinical specimens to prepare viruses for vaccines to research the biology of viruses

The negative (-) sense strand of RNA _______.

to synthesize more + strands

True or false: All viruses must infect a host cell in order to replicate.

true

The process of _____ occurs when viruses lose their envelope during penetration into a host cell or when the envelope/capsid is are dissolved within a vacuole.

uncoating

Which term describes the process of a virus losing its capsid and exposing viral nucleic acids to the immediate environment?

uncoating

Viruses were discovered by ______.

using a filter

The first event to occur in the release of an enveloped virus is the _______.

viral spike proteins are inserted into host cell membrane.

A single virus particle is known as a(n)

virion

Identify the smallest pathogenic agent.

virion

Which of the following is composed of only RNA?

viroid

The term "in _______ " implies that a virus is being propagated in a living animal.

vivo