Viruses test

b, c, d, a
Put the following terms in order, from simplest to most complex: a. virion b. capsomere c. capsid d. nucleocapsid
It infects many kinds of cells in many different hosts.
Which of the following statements describes a generalist virus?
it does not perform the physiological functions carried out by the cytoplasmic membrane
The envelope found in some virus particles differs from the cytoplasmic membrane of cells in that _____.
Viruses enter a cell to complete the replication they have begun extracellularly.
Which of the following statements concerning viruses is FALSE?
protection and recognition
The outermost layer of a virion fulfills which of the following functions of the virus?
a nucleic acid.
During the intracellular state, a virus exists as
type of nucleic acid.
Viruses are primarily classified according to their
interactions between viral and cellular surface molecules.
Host specificity of a virus is due to
Ivanowsky
Who was the first person to demonstrate the existence of viruses?
they have no extracellular state.
How are fungal viruses different from viruses that infect other organisms?
envelope
Which of the following would NOT be found as a component of a bacteriophage?
in both cells and viruses.
A lipid membrane is present
in both cells and viruses.
Double-stranded DNA genomes are found in
only in viruses.
Double-stranded RNA genomes can be found in
cells only.
Cytoplasm is a characteristic of
both cells and viruses.
Proteins are present in
True
Most viruses cannot be seen by light microscopy.
True
Protozoa are susceptible to viral attack.
Their nucleic acids are injected into the cell.
How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
+RNA viruses
Which virus employs the use of an RNA-dependent RNA polymerase?
Retroviruses
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
Enveloped viruses
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane?
+RNA
Which of the following can be used directly as messenger RNA?
They require a host in order to reproduce.
How are viruses different from cells?
To package and protect the viral genome
What is the function of the structural elements of a virus?
a prophage.
Lysogenic viral DNA integrating into the host genome is referred to as
Exposure to UV light
Which of the following events might trigger induction of a temperate bacteriophage?
The host cell dies during the lytic stage.
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
It is copied every time the host DNA replicates.
What is the fate of the prophage during the lysogenic stage?
Penetration
In which stage is the viral DNA introduced into the cell?
Assembly
In which stage does formation of mature viruses occur?
Biosynthesis
The host DNA is usually degraded during which stage?
The virus would not be able to infect new hosts.
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
lysogenic conversion
Because lysogeny involves the integration of phage genes into the genome of the host cell, this can be a powerful mechanism for changing the phenotype of a bacterial strain.
Bacteriophage genes that cause toxin production in a normally harmless bacterial species are an example of _____.
the infected cell may live for a long time
Because enveloped viruses are shed slowly and persistently from the host cell by budding, the host cell may survive for a long time.
Infections with enveloped animal viruses are similar to lysogenic phage infections because _____.
cellular DNA polymerase
Most dsDNA viruses do not require any kind of special enzyme for their replication because they are able to utilize the normal enzymes and processes of the host cell.
Which of the following types of enzymes is necessary for the replication of most double-stranded DNA (dsDNA) viruses?
synthesis
During the synthesis stage of the lytic replication cycle, bacteriophages take over the synthetic processes of the cell by degrading the host cell’s DNA and directing protein synthesis from the viral genome.
Which of the following is the midpoint of a lytic replication cycle?
III, V, I, II, IV
Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
I. Synthesis
II. Assembly
III. Attachment
IV. Release
V. Entry
random collisions, chemical attractions, and receptor specificity
Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?
retroviruses
Reverse transcriptase is associated with which of the following?
the nuclear and cytoplasmic membranes and the endoplasmic reticulum
Which of the following membranes can give rise to a viral envelope?
persistent infection
Viruses are shed slowly and steadily during
latency
During ____, viruses remain dormant in a cell.
lytic
Virus replication results in the death of the cell in a(n) ______ infection.
Budding
is a mechanism of release for enveloped viruses.
True
Bacteriophages are cheaper and easier to culture than animal viruses.
inactivation of an oncogene
Either the activation of tumor repressor genes or the inactivation of oncogenes would be an appropriate mode of action for a new anticancer drug.
Which of the following would be an appropriate mode of action for a new anticancer drug?
disrupting cell division controls
Viruses and carcinogenic chemicals both cause tumors by interfering with the normal cellular controls over division and growth.
Both viruses and carcinogenic chemicals can cause tumors by _____.
metastasis.
Tumors invade other organs and tissues in a process called
oncogenesis
Virus infection results in cancer in the process of
False
Viruses cause most human cancers.
have been prepared in embryonated chicken eggs
Embryonated chicken eggs are an excellent way to grow many viruses, but when these virus preparations are used as the basis for vaccines, they can cause allergic reactions in some individuals.
Some people are allergic to certain types of vaccines because these vaccines _____.
different strains have various kinds of genetic abnormalities
HeLa cells have lost some of their original characteristics, resulting in a number of different strains. Therefore, they are regarded as a semistandard tissue culture medium.
HeLa cells are regarded as a semistandard human tissue culture medium because _____.
20
By counting the number of plaques on a plaque assay plate, a microbiologist can estimate the number of phage particles in the original mixture, since each plaque on the plate corresponds to a single phage.
In a plaque assay, a microbiologist counts 20 plaques on a plate. How many phage particles can be assumed to have been present in the original bacterium-virus mixture on the plate, if there was no dilution of the mixture prior to plating?
estimating the number of phages in a culture.
Plaque assays are used for
False
Virus vaccines are always cultured in embryonated chicken eggs.
assisting in normal synaptic development and function.
The normal function of the PrP protein in mammals is believed to be:
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
How do normal prion proteins (PrP) differ from the infectious prion proteins?
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
How does the number of infectious prions increase?
The multimers are more stable and resistant to protease.
Why are the beta-pleated multimers of PrP potentially pathogenic?
Chronic wasting disease
Which of the following prion diseases is found in deer and elk?
Kuru
Which of the following prion diseases was also known as laughing disease?
Variant Creutzfeldt-Jakob disease
Which of the following conditions in humans is linked to bovine spongiform encephalopathy?
Thalamus
What part of the nervous system is most affected by fatal familial insomnia?
The prion disorder causes infected sheep to scrape against objects until their skin is raw.
Where does the name “scrapie” come from?
Proteinaceous infectious particles
From which phrase is the term “prions” derived?
1982
In what year did Stanley Prusiner discover prions?
Scrapie
Which disease did Stanley Prusiner first identify as being caused by prions?
They lack nucleic acid.
How are prions different from other infectious agents?
Hodgkin’s lymphoma
Hodgkin’s lymphoma is a virally induced form of cancer.
Which of the following diseases is NOT caused by prions?
Hodgkin’s lymphoma
bovine spongiform encephalitis
scrapie
kuru
they do not contain rRNA
Prions do not contain nucleic acids, so conventional genetic analyses involving molecules such as rRNA are not applicable.
Conventional genetic analyses of prions involving rRNA sequences are impossible because _____.
plants
Viroids infect
they lack nucleic acid.
How are prions different from all other known infectious agents?
an envelope is acquired during budding through a host cell’s membrane
As virions are assembled, they are released, via a process called budding, through one of the cell’s membranes-the nuclear, endoplasmic reticulum, or the cytoplasmic membrane. Each virion then acquires a portion of membrane, which becomes the viral envelope.
The Clinical Case Follow-Up reveals that the African village has been afflicted with Ebola hemorrhagic fever caused by Ebola virus. This virus is an enveloped virus that acquires its outer covering when ___________________________.
its genomic RNA must be copied by viral RNA-dependent RNA transcriptase into a positive strand
In order to synthesize a protein, a ribosome can use only mRNA because -RNA is not recognized by ribosomes. The virus overcomes this problem by carrying RNA-dependent RNA transcriptase, which is released into the host cell’s cytoplasm during uncoating and then transcribes RNA molecules from the virus’s -RNA genome. Translation of proteins can then occur as usual.
The genome of Ebola virus is a negative-sense, single-stranded RNA molecule. When this virus replicates, _____________________.
on host ribosomes in the cytoplasm
RNA viruses are replicated in the cytoplasm.
Ebola virus, which has an RNA genome, infects endothelial cells that line blood vessels. Within these infected cells, synthesis of viral proteins takes place ___________________.

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