Viruses are primarily classified according to their?
During the intracellular state, a virus exists as?
a nucleic acid
During _____________, viruses remain dormant in a cell.
Which of the following can give rise to a viral envelope?
A the cytoplasmic membrane B the cristae of mitochondria C the endoplasmic reticulum D all of the above A
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?
Host specificity of a virus is due to?
interactions between viral and cellular surface molecules.
Put the following stages of a lytic replication cycle in order, from earliest to latest stages:
A V, III, II, IV, I B III, V, I, II, IV C I, III, V, II, IV D III, II, V, I, IV E I, II, III, V, IV B
Which of the following infectious particles do not have protein in their structure?
A bacteriophages B animal viruses C viroids D prions E both prions and viroids C
Lysogenic viral DNA integrating into the host genome is referred to as
A lysogeny. B induction. C a prophage. D lytic. C
Which of the following events might trigger induction of a temperate bacteriophage?
A An infected cell entering the logarithmic phase of growth B Normal cell division of an infected cell C Exposure to UV light D Bacterial conjugation C
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
A The host cell can only divide during the lytic stage. B The host cell is allowed to live during the lytic stage. C The host cell dies during the lytic stage. D The viral DNA may integrate into the host genome during the lytic stage. C
What is the fate of the prophage during the lysogenic stage?
A It is packaged into viral proteins and maintained until the host is exposed to an environmental stress. B It is degraded by the activity of host defense enzymes. C It is copied every time the host DNA replicates. D It is released from the cell by lysing the cell. C
How are prions different from all other known infectious agents?
A they lack nucleic acid. B they cannot reproduce outside a cell. C they can be destroyed by incineration. D they act as slow viruses. E they cause neurological problems. A
Which of the following types of enzymes is necessary for the replication of most double-stranded DNA (dsDNA) viruses?
A reverse transcriptase B RNA-dependent RNA transcriptase C viral RNA polymerase D cellular DNA polymerase D
Most viruses cannot be seen by light microscopy. T/F
Why is lysogeny advantageous to a bacteriophage?
A it enables the bacteriophage to take over the cell. B the genetic material of the bacteriophage can be passed on to future generations of cells. C it speeds up the viral infection cycle. D it allows the bacteriophage to destroy the host cell's DNA. E it allows the bacteriophage to infect cells it would not normally infect. B
Most viral genomes are much smaller than the genomes of the cells they infect. Which of the following CANNOT be inferred from this statement?
A Viral genomes can be enclosed in very small capsids. B Most viruses can infect only certain types of cells. C Viral genomes usually contain fewer genes than cellular genomes. D Viral genomes usually do not encode all of the enzymes or structures necessary for their replication. B
How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
A They uncoat after they enter the cell. B Their DNA attaches to receptors on the cell surface. C Their nucleic acids are injected into the cell. D Their protein coat fuses to the cell membrane. C
Which virus employs the use of an RNA-dependent RNA polymerase?
A +RNA viruses B dsDNA viruses C ssDNA viruses D Retroviruses A
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane?
Which of the following can be used directly as messenger RNA?
A -RNA B ssDNA C +RNA C
Both viruses and carcinogenic chemicals can cause tumors by
A killing cells. B slowing cellular growth. C creating new cellular genes. D disrupting cell division controls. D
Which of the following agents is capable of inducing conversion of a lysogenic virus back to a lytic virus?
A stress B UV light C pH D all of the above D
The genome of which of the following types of animal virus can act directly as mRNA?
A retroviruses B +ssRNA viruses C dsRNA viruses D -ssRNA viruses E ssDNA viruses B
Reverse transcriptase is associated with which of the following?
In which stage is the viral DNA introduced into the cell?
In which stage does formation of mature viruses occur?
The host DNA is usually degraded during which stage?
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
The virus would not be able to infect new hosts.
Double-stranded RNA genomes can be found in
only in viruses
Protozoa are susceptible to viral attack.T/F
How are viruses different from cells?
A They do not contain protein. B They do not contain genetic material. C They require a host in order to reproduce. D They do not contain enzymes. C
What is the function of the structural elements of a virus?
A To package and protect the viral genome B To use all of the cell proteins C To provide a source of energy for the virus A
A(n) ________ is a clear zone on a bacterial lawn where cells have been killed by the activity of a bacteriophage
Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?
A retroviruses B +ssRNA viruses C ssDNA viruses D -ssRNA viruses E dsDNA viruses D
____________________is a mechanism of release for enveloped viruses.
Double-stranded DNA genomes are found in
both cells and viruses
The envelope found in some virus particles differs from the cytoplasmic membrane of cells in that
A it does not perform the physiological functions carried out by the cytoplasmic membrane. B it contains different types of phospholipids than a cytoplasmic membrane. C it is not as flexible as a cytoplasmic membrane. D it is not as dense as a cytoplasmic membrane. A