Mmb microbiology chapter 13

Which of the following is an accurate description of a virion?

a population of infectious particles
an infectious particle of protein and nucleic acid outside a host cell
the nucleic acid of a viral pathogen
the protein portion of a viral particle
the nucleic acid of a viral pathogen inside a host cell

The outermost layer of a virion fulfills which of the following functions of the virus?

protection
replication
recognition
both protection and recognition
both recognition and replication

A ________ is a virus that infects bacterial cells.

prion
nucleocapsid
bacteriophage
virion
viroid

Which of the following is present in cells only during virus infection?

DNA-RNA heteroduplex
ssRNA
triplet RNA
ssDNA
dsDNA

Host specificity of a virus is due to

particular genes that it shares with the infected cell.
the presence of an envelope.
the presence or absence of a cell wall on the host cell.
differences in size between the virus and the host cell.
interactions between viral and cellular surface molecules.

The shape of a virion is a function of the ________ of the virus.

type of genome material
capsid
cell type of the host cell
size of the genome material
envelope

How are fungal viruses different from viruses that infect other organisms?

they have only DNA for genetic material.
they have no intracellular state.
they have no extracellular state.
they cannot pass through a filter.
they have no capsid.

The envelope portion of an enveloped virus is composed of

glycolipids of the host cell.
host glycolipids and virus-encoded glycoproteins.
host cell membranes containing virus-encoded glycoproteins.
phospholipids from host cell membranes.
virus-encoded glycoproteins.

Which of the following may occur in a lysogenic infection, but NOT a latent one?

The inserted viral DNA may leave the host DNA.
The provirus/prophage directs the synthesis of viral proteins.
The prophage/provirus alters gene expression in the host cell.
The prophage/provirus is replicated with the host DNA.
The viral DNA integrates (inserts) into the host cell DNA.

Which of the following statements regarding virus taxonomy is TRUE?

Some virus family names are derived from the name of an important member of the family.
Viruses are classified on the basis of the taxonomy of their host organisms.
Virus classes are well established.
Virus classes are based on the domain of the host organism.
The species epithet is a latin descriptor of the virion structure.

Classification of viruses includes

orders.
classes.
families.
orders and families.
classes, orders, and families.

What is the correct order for the stages of a lytic replication cycle, from earliest to latest stages?
I. Synthesis
II. Assembly
III. Attachment
IV. Release
V. Entry

III, V, I, II, IV
I, III, V, II, IV
I, II, III, V, IV
III, II, V, I, IV
V, III, II, IV, I

Which of the following is involved in the attachment of a bacteriophage to a bacterial cell?

chemical attractions
random collisions
receptor specificity
both chemical attractions and receptor specificity
random collisions, chemical attractions, and receptor specificity

The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?

synthesis
entry and release
assembly
entry
attachment

Naked capsid animal viruses gain entry to host cells by

endocytosis.
direct penetration.
membrane fusion.
both endocytosis and direct penetration.
endocytosis, direct penetration, and membrane fusion.

Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but not in the lysogenic cycle?

viral protein synthesis
attachment
entry
digestion of host DNA
both digestion of host DNA and viral proteins synthesis

Why is lysogeny advantageous to a bacteriophage?

it enables the bacteriophage to take over the cell.
the genetic material of the bacteriophage is amplified many times over that seen in a lytic phage.
it allows the bacteriophage to destroy the host cell’s DNA.
it speeds up the viral infection cycle.
it allows the bacteriophage to infect cells it would not normally infect.

Which of the following agents is capable of inducing conversion of a prophage to the lytic cycle?

presence of +ssRNA
UV light
X-rays
both UV light and X-rays
both UV light and the presence of +ssRNA

Zones of clearing in cell cultures that are the result of virus infection are called plaques. Sometimes “cloudy plaques” are seen on bacterial cultures infected with bacteriophage. What type of viral infection might cause this appearance?

lytic
transducing
lysogenic
viroid
prion

Which virus is CORRECTLY matched with its method of entry?

poliovirus; endocytosis
adenovirus; direct penetration
HIV; membrane fusion
measles virus; direct penetration
herpesvirus; membrane fusion

Retroviruses require the activity of ________ to complete their infection cycle.

viral RNA polymerase
RNA-dependent RNA transcriptase
lysozyme
RNA-dependent RNA polymerase
reverse transcriptase

The genome of which of the following types of animal virus can act directly as mRNA?

dsDNA
dsRNA viruses
ssDNA viruses
-ssRNA viruses
+ssRNA viruses

Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?

-ssRNA viruses
+ssRNA viruses
retroviruses
ssDNA viruses
dsDNA viruses

In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of the host cell. This fact implies that the viral genome may encode

RNA-dependent RNA transcriptase.
reverse transcriptase.
ribosome components.
a DNA polymerase.
reverse transcriptase and RNA-dependent RNA transcriptase.

Which of the following membranes can give rise to a viral envelope?

the cytoplasmic membrane
the endoplasmic reticulum
the nuclear membrane
the nuclear and cytoplasmic membranes
the nuclear and cytoplasmic membranes, and the endoplasmic reticulum

A cell is infected with a virus carrying an oncogene sequence in its genome. What process may occur if the oncogene is expressed in the infected cell?

lysis
lysogeny
neoplasia
latency
both lysis and neoplasia

How is the HIV provirus different from a lambda-phage prophage?

lambda phage-infected cells produce virus slowly over time.
the HIV provirus is integrated permanently into the host cell’s DNA.
all the offspring of a cell infected with a prophage will contain the virus.
all subsequent generations of HIV-infected cells carry the provirus.
the HIV provirus is inactive inside the host cell.

The process of metastasis results from

benign tumors.
neoplasia.
oncogene expression.
malignant tumors.
viral latency.

One mechanism by which viruses may cause cancer is to interrupt the genetic regulatory sequences of repressor proteins. Which of the following types of viruses is most likely to be involved in causing cancer by this mechanism?

+ssRNA viruses
dsRNA viruses
retroviruses
-ssRNA viruses
both +ssRNA and -ssRNA viruses

The development of a cancerous cell is said to require “multiple hits.” This means

multiple cell cycle regulators are inactivated at once.
a series of separate events over time lead to the loss of cell cycle regulation.
several protoncogenes are activated at the same time.
the cell must be infected with several different types of viruses to be transformed.
multiple oncogenic viruses infect the cell at the same time.

Plaque assays are used for

cultivating viruses that cannot be grown any other way.
evaluating the cancer-causing ability of a virus.
determining the density of phage in a culture.
counting the number of latent phages in a cell.
the study of prions.

Diploid cell cultures and continuous cell cultures differ in which of the following ways?

source of cells
convenience of use
longevity
both longevity and convenience of use
both longevity and source of cells

What is one of the most difficult aspects of studying animal viruses?

The viruses are extremely dangerous to handle.
The use of animals is expensive, and unethical to many people.
The use of animals to study the viruses is unethical in the eyes of many.
The study requires expensive facilities.
The viruses are hard to obtain.

How are prions different from all other known infectious agents?

they act as slow viruses.
they cause neurological problems.
they lack nucleic acid.
they can be destroyed by incineration.
they cannot reproduce outside a cell.

The viruses of fungi have RNA genomes and lack a capsid. They are therefore similar to

viroids.
enveloped viruses.
bacteriophages.
lysogens.
prions.

Infection with ________ is likely to result in destruction of the host cell by lysis.

viroids
prions
oncogenic viruses
naked viruses
enveloped viruses

Some human viruses are difficult to study because

very few laboratories have the skills to culture the viruses.
they establish latent infections and cannot be induced.
they grow very slowly.
they only grow in normal human cells.
the growth medium for the host cells is complex.

Why are diploid cell cultures preferred over continuous cell cultures?

Results from continuous culture cells do not apply to disease in whole organisms.
Diploid cells last far longer than continuous culture cells.
Continuous cell cultures are expensive to maintain.
Diploid cells have undergone changes in their chromosome structure that make them more stable.
Diploid cells are more nearly like cells of whole organisms than continuous culture cells.

Which of the following is a feature shared by viruses and living organisms?

the ability to increase in size
presence of cytoplasm
possession of a genome that directs synthesis of materials necessary for replication
metabolic capability
responsiveness

Small circular RNA molecules without capsids are characteristic of

viruses.
viroids.
plasmids.
prions.
viruses and prions.

Prions cause disease in

fungi.
mammals.
bacteria.
birds.
plants.

During ________, viral synthesis is suspended.

oncogenesis
budding
latency
lytic replication
persistent infection

Virus replication results in the death of the cell in ________ infection(s).

a lytic
a lysogenic
a persistent
a latent
both latent and persistent

A ________ is a mass of neoplastic cells.

metastasis
tumor
plaque
diploid culture
gall

The process known as ________ is a mechanism of release for enveloped viruses.

metastasis
persistent infection
latency
budding
lytic replication

Viruses cause most human cancers.

True
False

Virus entry requires the presence of specific cell structures.

True
False

Protozoa are susceptible to viral attack.

True
False

Many diseases of plants are caused by infectious RNA molecules lacking capsids.

True
False

All members of a virus family have the same type of genome structure.

True
False

Assembly of new viruses is a process that usually requires the direction of a variety of viral and cellular enzymes.

True
False

Bacteriophage release is a gradual process in which small numbers are released at a time.

True
False

Bovine spongiform encephalopathy is an example of a prion disease.

True
False

All viruses use the host cell’s nucleic acid polymerases for replication.

True
False

Fertilized chicken eggs are used to culture some vaccine strains.

True
False

The combination of a virus’s protein coat and nucleic acid core is called the (capsid/virion/nucleocapsid).

Assembly of enveloped viruses requires (membrane/matrix/receptor) to bring together the nucleocapsid and the envelope.

The first virus isolated, Tobacco mosaic virus, has a (complex/helical/polyhedral) capsid morphology, which facilitated its isolation.

Some viruses can be cultured on (continuous/diploid/animal) cells which are descended from neoplastic cells.

The virions shown in the figure have a (polyhedral/helical/complex) capsid.

Another term for a lysogenic phage is a (temperate/latent/prophage) phage.

The process in which viral capsids are removed within the infected cell is called (entry/disassembly/uncoating).

Uncontrolled cell division in animals is known as (metastasis/neoplasia/cancer).

The graph in the figure shows a pattern of virion abundance consistent with a (lytic/latent/persistent) virus infection cycle.

Viruses are responsible for (all/most/some) human cancers. (Use relative terms not numbers.)

Genes that play a role in proper cell division but may also play a role in some types of cancer are called (oncogenes/protooncogenes/promoters).

A (colony/plaque) is a clear zone on a bacterial lawn where cells have been killed by the activity of a bacteriophage.

Three (orders/families/classes) represent the highest level of taxonomic rank used in classifying viruses.

RNA dependent RNA polymerase is required for successful infection by (+ssRNA/-ssRNA/dsRNA) viruses.

An animal virus that does not have an envelope is described as a(n) (naked/unenveloped/capsid) virion.