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Which of the following statements describes a generalist virus? |
It infects many kinds of cells in many different hosts |
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All of these are steps in the lytic cycle of a temperate bacteriophage. Which happens second? |
1. attachment *2. ENTRY 3. bacterial chromosome degraded 4. synthesis 5. assembly 6. release |
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Which of the following is NOT represented in viral classification schemes? |
1. order 2. family 3. genus 4. specific epithet *class is NOT |
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Which of the following diseases is NOT caused by prions? |
1. Bovine Spongiform Encephalitis 2. Kuru 3. Scrapie *Chagas’ disease is NOT |
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Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4? |
Entry and Release |
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Conventional genetic analyses of prions involving rRNA sequences are impossible because __________. |
they do not contain nucleic acids |
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The envelope found in some virus particles differs from the cytoplasmic membrane of cells in that __________. |
it does not perform the physiological functions carried out by the cytoplasmic membrane (such as endocytosis or active transport) |
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Which of the following is an essential component of all viruses? |
a. ribosomes *b. capsid- all viruses have a capsid surrounding their nucleic acid c. envelope d. DNA |
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Lysogeny refers to…? |
viral DNA becoming imbedded within the host cell’s chromosomes. |
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Lysogeny is associated with all of the following EXCEPT… |
Animal viruses do not undergo lysogeny. |
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Put the following viral structures in order, from simplest to most complex: I. virion II. capsomere III. capsid IV. nucleocapsid |
capsomere capsid nucleocapsid virion |
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Viruses can be grown in all of the following EXCEPT __________. |
sterile nutrient agar- Viruses cannot be grown in sterile nutrient agar or other microbiological media because viruses must have a host cell present to reproduce. |
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You have isolated bacterium that contains a prophage. Which of the following is true concerning the prophage? |
The phage is in the lysogenic cycle |
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In a plaque assay, a microbiologist counts 20 plaques on a plate. How many plaque-forming units 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? |
20. Each plaque on the plate corresponds to a single phage. |
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Which of the following would be an appropriate mode of action for a new anticancer drug? |
inactivation of an oncogene |
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Which of the following types of enzymes is necessary for the replication of most double-stranded DNA (dsDNA) viruses? |
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. |
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Most viral genomes are much smaller than the genomes of the cells they infect. Which of the following CANNOT be inferred from this statement? |
b. Most viruses can infect only certain types of cells. |
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Which of the following is NOT a way in which viruses differ from all other living things? |
b. they live inside host cells |
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A phage T4 particle that has lost its tail fibers will have a replication cycle that is blocked at which of the following stages? |
attachment |
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Both viruses and carcinogenic chemicals can cause tumors by __________. a. killing cells |
disruption of cell division |
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Contact between a phage and its bacterial host occurs by _____. |
a random collision |
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What portion of bacteriophage T4 enters E. coli? |
Only the T4 genome enters the bacterial cell. |
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Once entry into the bacterial cell has been achieved, the next step in a lytic replication cycle is _____. |
Only the T4 genome enters the bacterial cell. |
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During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules? |
Phage enzymes degrade the bacterial DNA. |
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In a lytic cycle of replication, release of phages involves _____. |
the bacterial cell bursting open |
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A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____. |
the phage genome inserts itself into the host genome |
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What factor may induce a prophage to enter the lytic cycle? |
UV light |
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During the lysogenic cycle, it is possible for integrated phage genes to change the characteristics of the host cell. This is known as _____. |
lysogenic conversion |
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How are viruses different from cells? |
They require a host in order to reproduce. |
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What is the function of the structural elements of a virus? |
to package and protect the viral genome |
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Lysogenic viral DNA integrating into the host genome is referred to as |
a prophage |
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Which of the following events might trigger induction of a temperate bacteriophage? |
exposure to UV light |
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How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell? |
the host cell dies during the lytic stage |
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What is the fate of the prophage during the lysogenic stage? |
it is copied every time the host DNA replicates |
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We sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. This renders the virus unable to reproduce. Which step of viral replication are antibodies directly preventing? |
attachment |
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Enveloped viruses have a layer of lipids surrounding their capsid. This envelope is made mostly of host cell membrane. In which step does the virus acquire this envelope? |
release |
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What occurs during viral uncoating? |
the capsid breaks apart |
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The normal function of the PrP protein in mammals is believed to be: |
assisting the normal synaptic development and function |
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How do normal prion proteins (PrP) differ from the infectious prion proteins? |
normal PrP have alpha-helicases; infectious PrP have beta-pleated sheets |
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How does the number of infectious prions increase? |
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion. |
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Why are the beta-pleated multimers of PrP potentially pathogenic? |
The multimers are more stable and resistant to protease |
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From which phrase is the term "prions" derived? |
Proteinaceous infectious particles |
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How are prions different from other infectious agents? |
they lack nucleic acid |
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The infectious cycles of enveloped animal viruses and temperate bacteriophages are most similar because __________. |
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. |
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