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Q:
Viral proteins are categorized as early, middle, and late. Early proteins typically are necessary for
A) production of viral mRNA.
B) packaging of DNA into the nucleocapsid.
C) copying the viral genome.
D) production of viral mRNA and copying the viral genome.
Q:
Which of the following samples would contain the MOST genetic diversity?
A) viral metagenomes from the ocean
B) bacterial metagenomes from the ocean
C) microbial eukaryotic metagenomes from the ocean
D) viral metagenomes from human red blood cells
Q:
In E. coli, the adenine in the sequence GATC is methylated by the Dam enzyme. In the same cells a restriction endonuclease recognizes and cleaves dsDNA with GATC on either strand. Why does E. coli have these two enzymes?
A) The enzymes cut the E. coli genome into pieces that bind to viral particles and inhibit viral replication.
B) The enzymes increase the rate of mutation and genome rearrangement, thus increasing the likelihood that E. coli cells will mutate and become resistant to viral infection.
C) The enzymes encourage lysogeny because the cleavage sites are recognized by viral integrases.
D) The enzymes protect E. coli from infection by preferentially degrading viral or other exogenous DNA that is not methylated.
Q:
The T4 phage protects its DNA from host restriction endonucleases by
A) glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
B) methylating all four bases (A, T, C, G) in the T4 genome to prevent DNA cleavage.
C) integrating the viral genome into the host genome where it will not be degraded.
D) circularizing the viral genome so that it will not be degraded.
Q:
T4 genes are transcribed by host RNA polymerase, yet the transcription of T4 genes is carefully controlled so that groups of T4 genes are transcribed at specific times after infection. How is this accomplished?
A) Early T4 genes encode for proteolytic enzymes that destroy the host RNA polymerase. Subsequently a viral polymerase is created that transcribes the middle and late genes in the correct order.
B) Early and middle T4 genes encode for proteins that modify the activity of sigma factors and host RNA polymerase to regulate the expression of T4 genes.
C) Each group of T4 genes has a different promoter that indicates that order in which they should be transcribed in based on the affinity of the promoter for the host RNA polymerase.
D) Rolling circle replication of the viral genome ensures that the genes are available for transcription in the correct order.
Q:
When solutions of host cells and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.
A) insertion sequences
B) plaques
C) prophages
D) colonies
Q:
The use of ________ is the easiest and most effective way of studying many animal and plant viruses.
A) bacterial cultures
B) tissue or cell culture
C) live hosts
D) prophages
Q:
Virions infecting some bacteria possess the enzyme ________ that makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
A) peptidoglycanase
B) infectase
C) lysozyme
D) nuclease
Q:
Regarding the viral membrane of an enveloped virus, the lipids are derived from the ________, and the proteins are encoded by ________.
A) host's cell membrane / viral genes
B) virion / viral genes
C) host's cell membrane / host's genes
D) virion / host's genes
Q:
You are attempting to mutate lambda to affect whether lysis or lysogeny occurs after lambda infection. Which mutation would INCREASE the chances of LYSOGENY over lysis?
A) deletion or inactivation of the cI gene
B) deletion or inactivation of the cro gene
C) overexpression of the cro gene
D) deletion of both the cro and cI genes
Q:
The size and shape of viral particles is largely governed by the size and packaging of the viral
A) envelope.
B) enzymes.
C) prophage.
D) genome.
Q:
The term "phage" is generally reserved for the viruses that infect
A) animals.
B) plants.
C) bacteria.
D) multiple species.
Q:
When a virus enters a host cell in which it can replicate, the process is called a(n)
A) insertion.
B) infection.
C) prophage.
D) excision.
Q:
What genome composition makes viruses most susceptible to destruction by prokaryotic restriction endonucleases?
A) dsDNA
B) ssDNA
C) dsRNA
D) ssRNA
Q:
Bacteriophage have a ________ complex structure than animal viruses, because ________.
A) more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cells
B) less / the bacteriophage does not have to penetrate the nucleus
C) more / the bacteriophage must penetrate the peptidoglycan cell wall
D) less / there prokaryotic cells have a simple structure compared to eukaryotic cells
Q:
Which of the following are the hosts for most enveloped viruses?
A) Bacteria
B) animals
C) Archaea
D) fungi
Q:
When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus
A) capsid.
B) concatemer.
C) nucleocapsid.
D) envelope.
Q:
The consequence of an infection by a temperate bacteriophage is that the bacterial cell
A) lyses before it gets a chance to divide.
B) never lyses but continues to divide and replicate both the virus and the cell.
C) divides faster at moderate temperatures.
D) may lyse before it divides or may continue to divide and replicate both the virus and the cell.
Q:
Rolling circle replication of the lambda genome differs from replication of a bacterial chromosome in that
A) bidirectional replication forks are not formed.
B) only a single strand of the genome is copied.
C) no concatamers are formed.
D) only a single strand of the genome is copied and no concatamers are formed.
Q:
The primer for retrovirus reverse transcription is a specific
A) tRNA encoded by the cell.
B) tRNA encoded by the virus.
C) nuclear tRNA.
D) nuclear tDNA.
Q:
Retroviruses are medically important viruses because
A) they include the viruses the cause hepatitis.
B) some retroviruses cause cancer.
C) they include the virus that causes AIDS.
D) they include viruses that cause cancer and AIDS.
Q:
Which of the following statements is TRUE?
A) Lambda is a temperate phage that infects Escherichia coli.
B) Lambda is a linear double-stranded DNA phage.
C) Lambda is replicated by the rolling circle mechanism.
D) Lambda is a temperate phage that replicates its double-stranded DNA genome with a rolling circle mechanism.
Q:
The virus repressor protein
A) controls the prophage's lytic genes but not the incoming genomes of the same virus.
B) does not control the prophage's lytic genes but does control the incoming genomes of the same virus.
C) controls both the lytic genes on the prophage and prevents an incoming virus of the same type.
D) has different actions in different situations.
Q:
A prophage replicates
A) along with its host while the lytic genes are expressed.
B) along with its host while the lytic genes are not expressed.
C) independently of its host while the lytic genes are expressed.
D) independently of its host while the lytic genes are not expressed.
Q:
The packaging mechanism of T4 DNA involves cutting of DNA from
A) linear genetic elements.
B) circular genetic elements.
C) DNA concatemers.
D) its host cells.
Q:
Which of the following enzymes would you expect to find in the virion of a retrovirus, but NOT in a bacteriophage?
A) lysozyme
B) methylase
C) restriction enzymes
D) reverse transcriptase
Q:
A virus that kills its host is said to be
A) lytic or virulent.
B) temperate.
C) lysogenic.
D) virulent or lysogenic, but not temperate.
Q:
Bacteriophages' genomes are typically composed of
A) single-stranded RNA.
B) single-stranded DNA.
C) double-stranded RNA.
D) double-stranded DNA.
Q:
Based on your knowledge of cellular and viral processes, which of the following would be (an) appropriate target(s) for antiviral drugs?
A) integrases
B) aminoacyl-tRNA synthetases
C) ribosomes
D) aminoacyl-tRNA synthetases and ribosomes
Q:
The discovery of retroviruses changed our understanding of
A) gene structure and organization.
B) the flow of genetic information.
C) protein synthesis.
D) infectious particles.
Q:
Restriction is
A) the viral process whereby a host's DNA ceases normal functioning.
B) the viral process whereby the virus prevents other viruses from entering the cell.
C) a general host mechanism to prevent the invasion of foreign nucleic acid.
D) a general host mechanism to prevent virus particles from further infective action.
Q:
Cellular receptors may be composed of
A) proteins.
B) carbohydrates.
C) lipids.
D) combinations of proteins, carbohydrates, and/or lipids.
Q:
ALL viral particles
A) are metabolically inert.
B) are smaller than bacterial cells.
C) contain an envelope to prevent its degradation outside of a host.
D) exhibit cell lysis under a particular condition.
Q:
Viruses infecting ________ are typically the easiest to grow in the laboratory.
A) plants
B) animals
C) fungi
D) prokaryotes
Q:
Reverse transcriptase is a(n)
A) RNA-dependent DNA polymerase.
B) DNA-dependent DNA polymerase.
C) RNA-dependent RNA polymerase.
D) DNA-dependent RNA polymerase.
Q:
Which statement is TRUE?
A) All viruses contain their own nucleic acid polymerases.
B) Many viruses contain their own nucleic acid polymerases.
C) Viruses do not contain their own nucleic acid polymerases.
D) The origins of the nucleic acid polymerases used by viruses are eukaryotic.
Q:
Enveloped viral membranes are generally ________ with associated virus-specific ________.
A) lipid bilayers / phospholipids
B) protein bilayers / lipids
C) lipid bilayers / glycoproteins
D) glycolipid bilayers / phospholipids
Q:
Viral size is generally measured in
A) micrometers.
B) picometers.
C) nanometers.
D) centimeters.
Q:
Viral replication occurs
A) intracellularly.
B) extracellularly.
C) both intracellularly and extracellularly.
D) either intracellularly or extracellularly, depending on the virus involved.
Q:
Viral replication is
A) independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.
B) independent of both the host cell's DNA and the host cell's enzymes and metabolism.
C) dependent on the host cell's DNA and RNA.
D) dependent on the host cell's DNA, RNA, enzymes, and metabolism.
Q:
Transcriptional regulators bind most frequently at the ________ site of DNA.
A) major groove
B) minor groove
C) histone complex
D) primary supercoil
Q:
A protein region with a specific function and structure is called a
A) conserved site.
B) domain.
C) locale.
D) motif.
Q:
Regulatory proteins
A) are influenced by small molecules.
B) bind to specific DNA sites.
C) regulate transcription.
D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules.
Q:
When arginine is added to a culture growing exponentially in a medium without arginine, what occurs?
A) All cellular growth ceases.
B) Growth continues, but the production of enzymes required for the synthesis of arginine ceases.
C) Growth continues, but the production of enzymes required for the synthesis of arginine increases.
D) The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine.
Q:
Regulation of an enzyme's activity occurs
A) transcriptionally.
B) translationally.
C) posttranslationally.
D) at any point on the enzymatic production pathway.
Q:
Provide evidence that supports the hypothesis that riboswitches are remnants of the RNA world when catalytic RNAs were the only self-replicating life forms.
Q:
Explain why cellular cannibalism is beneficial for sporulating Bacillus subtilis.
Q:
In considering the function of heat shock proteins, why is it not a surprise that these proteins are both highly conserved and very ancient? Provide your reasoning.
Q:
A cocktail of 30 compounds was identified to harbor a corepressor, and subsequent separation and purification was performed to test individual compounds. Describe an experiment that would enable you to identify the specific compound that acts as a corepressor for a catabolic pathway. Be certain to explain what will be measured and how you could conclude which compound is a corepressor.
Q:
Explain the function of cAMP in catabolite repression.
Q:
Contrast prokaryotic and eukaryotic regulation of gene expression.
Q:
How is transcription in Archaea controlled?
Q:
Explain why one cell of a pathogenic bacterium by itself typically does not secrete a toxin, despite the species as a whole being characterized as toxin producing. To help in your explanation, predict what would happen to an individual pathogen that secreted a toxin inside a human.
Q:
Defend why is it unsurprising that two-component regulatory systems are all but absent in bacteria that live at the expense of a host?
Q:
Explain the sequence of events that would follow the transfer of an organism from a complex medium to a minimal medium.
Q:
Illustrate and explain an operon that is subject to both positive and negative control containing the operator region, the operon, the promoter, the activator binding site, and the functional genes in a DNA sequence. Also compare and contrast the roles activators and repressors have in regulating the illustrated operon.
Q:
Explain why regulation of enzyme synthesis is more time consuming than regulation of enzymatic activity.
Q:
Compare and contrast chemical, spatial, and temporal gradients as found in bacterial regulatory systems.
Q:
Describe the basic two-component regulatory system, and compare the function of each component.
Q:
Explain the phenomenon known as diauxic growth. Hypothesize why this type of regulation might be important for survival of a microbe in a community as well as a situation where lacking it might be advantageous.
Q:
Explain the translational attenuation mechanism.
Q:
Using the tryptophan operon as a model, explain a transcription pause site and the formation of a stem-loop.
Q:
Describe the function and the functional components of the maltose regulon system.
Q:
How is the leucine zipper formed, and what is its function?
Q:
What is the difference between an operator and a promoter?
Q:
Multiple mechanisms for small RNA (sRNA)-mediated translational regulation exist but all are unified by inactivating protein synthesis of the target mRNA.
Q:
Heat shock proteins are produced at high numbers to minimize damaging effects during high heat conditions as well as other stress signals unrelated to heat such as ultraviolet radiation.
Q:
Multiple sigma factors are essential to induce the biosynthesis of endospores, all of which are encoded by genes, so a complex regulatory mechanism such as this likely has a higher chance of mutations leading to incorrect functioning compared to a simple repression mechanism.
Q:
During chemotaxis, attractants increase the rate of autophosphorylation whereas repellants decrease this rate.
Q:
Quorum sensing requires a strong gradient to be reached before the signaling molecules are transported into the cytoplasm.
Q:
In catabolic repression, cells use the least abundant carbon source first.
Q:
In most cases, the first product of a particular biosynthetic pathway represses the enzymes of the pathway.
Q:
Once cytoplasmic sensor proteins involved in chemotaxis regulation are phosphorylated, a cascade of other phosphate-transferring mechanisms provide ATP energy to rotate flagella.
Q:
Cyclic AMP (cAMP) is involved in the global regulation of catabolic pathways in Escherichia coli, including the lac operon, and a low activity of adenylate cyclase that makes cAMP is suggestive of catabolite repression.
Q:
DNA-binding proteins typically affect translation of a protein.
Q:
A two-component regulatory system usually involves both the sensor and response proteins being subject to phosphorylation.
Q:
Studying the transcriptional activity of flagellar genes would not likely reveal differential changes when the cells are actively motile compared to nonmotile activity, because a two-component regulatory system is sufficient to control flagellar activity.
Q:
Proteins and RNA molecules that are needed in the cell, at about the same level under all growth conditions, require constitutive expression.
Q:
The preferential use of glucose over other available carbon substrates for growth is mechanistically explained by catabolite repression.
Q:
Transcriptional regulation is considered negative when an inducer binds to and deactivates a repressor.