Which of the following statements concerning viruses is FALSE?
Viruses enter a cell to complete the replication they have begun extracellularly
The outermost layer of a virion fulfills which of the following functions of the virus?
protection and recognition
During the intracellular state, a virus exists as
a nucleic acid
Viruses are primarily classified according to their
type of nucleic acid
Host specificity of a virus is due to
interactions between viral and cellular surface molecules
Who was the first person to demonstrate the existence of viruses?
Ivanowsky
How are fungal viruses different from viruses that infect other organisms?
They have no extracellular state
Which of the following infectious particles do NOT have protein in their structure?
viroids
Which of the following would NOT be found as a component of a bacteriophage?
envelope
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.
Which of the following statements comparing virus classification and taxonomy of organisms is true?
Genus and specific epithet are used in both classification systems
Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
Attachment, Entry, Synthesis, Assembly, and Release
Which of the following is associated with the attachment of a
bacteriophage to a bacterial
cell?
random collisions, chemical attractions, and receptor specificity
The enzyme lysozyme is critical for which of the stages of a bacteriophage T4 infection cycle?
entry and release
The phenomenon of transduction is associated with which of the stages of a bacteriophage infection cycle?
assembly
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but NOT in the lysogenic cycle?
digestion of host DNA
Why is lysogeny advantageous to a bacteriophage?
The genetic material of the bacteriophage can be passed on to future generations of cells
Which of the following agents is capable of inducing conversion of a prophage back to a lytic phage?
UV light and X rays
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?
lysogenic
Which of the following is matched INCORRECTLY?
adenovirus — membrane fusion
Reverse transcriptase is associated with which of the following?
retroviruses
The genome of which of the following types of animal virus can act directly as mRNA?
+ssRNA viruses
Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?
-ssRNA 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
a DNA polymerase
Which of the following membranes can give rise to a viral envelope?
the nuclear and cytoplasmic membranes and the endoplasmic reticulum
The majority of cases of infant diarrhea are caused by what kind of virus?
dsRNA viruses
How is the HIV provirus different from a lambda phage prophage?
The HIV provirus is integrated permanently into the host cell's DNA
Which of the following individuals discovered prions?
Prusiner
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?
retroviruses
Tumors invade other organs and tissues in a process called
metastasis
Plaque assays are used for
estimating the number of phages in a culture
Diploid cell cultures and continuous cell cultures differ in which of the following ways?
longevity and source of cells
Viroids infect
plants
How are prions different from all other known infectious agents?
They lack nucleic acid
The infectious particles of fungi have RNA genomes and lack a capsid. They are therefore similar to
viroids
A lipid membrane is present
in both cells and viruses
Double-stranded RNA genomes can be found
only in viruses
Cytoplasm is a characteristic of
Cells only
Proteins are present in
both cells and viruses
Viruses are shed slowly and steadily during
persistent infection
During __________, viruses remain dormant in a cell
latency
Virus replication results in the death of the cell in a(n) __________ infection
lytic
Virus infection results in cancer in the process of
oncogenesis
is a mechanism of release for enveloped viruses
Budding
Viruses cause most human cancers
FALSE
Most viruses cannot be seen by light microscopy
TRUE
Protozoa are susceptible to viral attack
TRUE
Many diseases of plants are caused by infectious RNA molecules lacking capsids
TRUE
Bacteriophages are cheaper and easier to culture than animal viruses
TRUE
Assembly of new viruses is a process that usually requires the
direction of a variety of viral
and cellular enzymes
FALSE
Bacteriophage release is a gradual process in which small numbers are released at a time
FALSE
Poxvirus is assembled in the cytoplasm of the cell instead of in the nucleus, as is the case for
TRUE
Transcription of RNA from RNA does not occur in uninfected cells
TRUE
Virus vaccines are always cultured in embryonated chicken eggs
FALSE