Chapter 5

A bird egg containing an embryo is useful for cultivation of animal viruses because it ____.

is a sterile environment and contains tissues that support viral multiplication

Identify all the components of the nucleocapsid.

nucleic acid and capsid

At minimum, all viruses are composed of

nucleic acids and proteins

Together, the capsid and nucleic acid of a virus are called the

nucleocapsid

Viruses that lead to cancer in infected hosts are called

oncogenic

Viruses have tropisms, that is they can infect

only cells of a certain tissue type

When a cell harbors a virus that is not immediately lysing the cell, it's known as what type of infection?

persistent infection

A clear area where virus-infected monolayers of cells have been disrupted or destroyed is called a(n)

plaque

An infectious agent made up of only protein and associated with spongiform encephalopathies is a(n)

prion

Capsomers are composed of

protein

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

reverse transcriptase

An enzyme that can synthesize DNA from RNA is called

reverse transcriptase

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

satellite virus

Most human viral infections are

self-limiting

Some laboratory animals can propagate viruses in the laboratory more readily than others because many viruses exhibit host

specificity

Which of the following diseases are caused by prions?

spongiform encephalopathy

Viruses are classified based on genetic makeup, chemical composition, and

structure

Virus cultivation is an important activity because viral stocks are needed for the preparation of some

vaccines

Antibiotics are effective at combating____but not____.

Bacteria;virus

Which of the following would indicate that a virus is infecting a tissue culture cell line?

Cells degenerate and lyse

A virus that has a membranous layer external to the nucleocapsid is called a(n)____virus

Enveloped

Budding is the release of_____viruses

Enveloped

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

False The viral envelope is composed of phospholipids while the capsid is composed of capsomer proteins.

This virus is in the adsorption stage of its life cycle, where it attaches to____from the host cell.

Membrane receptors

Cultured cells grow in the form of a_____,, a single confluent sheet of cells that supports viral multiplication.

Monolayer

Some animal viruses are called_____because they enter a host cell and permanently alter its genetic material, leading to cancer.

Oncogenic

ions in which cells harbor the virus but are not immediately lysed are called______infections.

Persistent

Besides viruses, two noncellular infectious agents known as____and viroids are medically important

Prions

Although the outer shell of viruses is made of_____, viruses lack the machinery to produce those shell components on their own

Protein

Which factor enables certain laboratory animals to propagate viruses more readily than others?

Receptor specificity between virus and particular animal hosts

Vhich is NOT a reason that eggs provide an excellent in vivo viral cultivation system?

The egg contains a tissue monolayer

Which is NOT a reason that eggs provide an excellent in vivo viral cultivation system?

The egg contains a tissue monolayer

Two terms that have the same meaning are cell culture and _____culture

Tissue

Which is most important for attachment of a virus to a host cell?

Viral specificity for host receptors

Plants are parasitized by virus-like agents composed of only naked strands of RNA thatlare called

Viroids

The part of the human microbiome that includes all of the viruses that are assoclated with the body is called the human

Virome

The type of penetration that occurs when viruses are taken into the cell followed by engulfment in a vacuole or vesicle is called

endocytosis

Naked viruses do not possess a(n)

envelope

The total nucleic acid content of a virus can be referred to as the viral _____.

genome

Which of the following term describes the total nucleic content of a virus?

genome

Which of the host cell structures must usually be specific for adsorption?

glycoprotein receptors

Viruses are best described as ________ rather than dead

inactive

Masses of viruses or damaged organelles of a cell due to a cytopathic effect of viral infection are called _______ bodies.

inclusion

Which of the following is a mass of viruses or damaged organelles caused by viral infection of a cell?

inclusion body

Change in a cell line monolayer is indicative of which of the following?

virally infected cells

Identify the smallest pathogenic agent.

virus

Two ways in which newly assembled viruses are released from host cells are through____or exocytosis by enveloped viruses, and through_____(rupture) by naked viruses

Budding Lysis/cell lysis

The structure directly surrounding the viral nucleic acid is the_____, a coat of proteins

Capsid

Viral DNA polymerase genes are expressed during the____stage of the synthesis phase of the viral life cycle.

Early

Which of these terms does not belong in this group?

Embryonic culture

All viruses have two parts: a____covering and____located in a central core

Protein:DNA or RNA

True or false: Most viral infections do not result in death of the host organism.

True

The viral process of attaching to the host cell receptor for the virus is called

adsorption

Which is the correct term to describe viral adherence to a host cell receptor?

adsorption

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

capsid

Which structure immediately encloses viral nucleic acid?

capsid

Which of the following is considered a monomer (a single unit) of a capsid?

capsomer

A protein subunit that forms the viral capsid is called a(n)

capsomere

Each viral capsid is constructed from identical subunits called ______.

capsomeres

Identical protein subunits that make up the viral capsid are called ______.

capsomeres

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

endocytosis

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

endocytosis

When observing a monolayer of cells, the areas where virus-infected cells have been destroyed show up as clear, well-defined patches called

plaques

Which term describes the process of a virus losing its capsid (and envelope, if it has one) and exposing viral nucleic acids to the immediate environment?

uncoating

process that occurs when viruses lose their capsid (and envelope, if they have one) during or after penetration into a host cell is called

uncoating

The complete set of viruses that are associated with the human body is termed the human _____.

virome

Viral DNA polymerase genes are expressed during the_____stage of the synthesis phase of the viral life cycle.

Early

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

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

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

envelope

Which agent is the cause of spongiform encephalopathy?

prion

Most host cell receptors that viruses attach to are actually ______ that the cell uses in normal function

proteins

Viruses can usually only adsorb to cells of specific tissue types and these specificities are called

tropisms

An infectious agent that lacks a capsid and merely consists of a strand of RNA is called a(n)

viroid

Which of the following is completely composed of RNA?

viroid

The limitation of the type of cell that a virus can invade is called the____range

Host

Some viral capsids are arranged in a three-dimensional 20-sided figure with 12 evenly spaced corners called a(n)

Icosahedron

Viruses have a compact and economical structure that is ______.

not cellular

Which of the following best describes a prion?

abnormal protein fibrils

Viruses are best described as ________ rather than alive

active

During the release stage of the viral multiplication cycle, enveloped viruses leave their host cells through ________, or exocytosis.

budding

click and drag on elements in order ist the correct order of viral life cycle phases, starting with the first at the top.

1. Adsorption 2. Penetration and Uncoating 3. Synthesis 4.Assembly 5. Release

a term "naked" used in describing viruses implies: the lack of.

A lipid envelope

Which of the following statements regarding protein synthesis is correct?

All viruses lack the machinery to synthesize proteins.

In viral multiplication, capsids and genetic material are packaged into virus particles during the_____step

Assembly

Mature virus particles are constructed from nucleic acid and protein during the____phase of the viral life cycle.

Assembly

New virions are built from their components during the_____phase of the viral life cycle

Assembly

One type of cytopathic effect is the accumulation of_____compacted masses of viruses or damaged cell organelles within an infected host cell.

Inclusion bodies

Viral capsid proteins are synthesized during the______stage of the synthesis phase of the viral life cycle.

Late

List 3 purposes of viral cultivation

To prepare vaccines ; To identify viruses in clinical specimens ; To study effects on host cells

Unlike organisms such as bacteria and protozoa, viruses:

are not cellular

During which phase of the viral life cycle are new virions built from their components?

assembly

A virus-like particle that is dependent on other viruses for replication is called a

satellite virus

What are the three main criteria used to classify viruses?

structure, chemical composition, and genetic makeup