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129 Cards in this Set

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Viral replication isA) 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.

independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.

Viral replication occursA) intracellularly.B) extracellularly.C) both intracellularly and extracellularly.D) either intracellularly or extracellularly, depending on the virus involved.

intracellularly.

Viral size is generally measured inA) micrometers.B) picometers.C) nanometers.D) centimeters.

nanometers.

Enveloped viral membranes are generally ________ with associated virus-specific ________.A) lipid bilayers / phospholipidsB) protein bilayers / lipidsC) lipid bilayers / glycoproteinsD) glycolipid bilayers / phospholipids

lipid bilayers / glycoproteins

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.

Many viruses contain their own nucleic acid polymerases.

6) 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.

A) RNA-dependent DNA polymerase.

Viruses infecting ________ are typically the easiest to grow in the laboratory.A) plantsB) animalsC) fungiD) prokaryotes

prokaryotes

ALL viral particlesA) 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.

are metabolically inert.

Cellular receptors may be composed ofA) proteins.B) carbohydrates.C) lipids.D) combinations of proteins, carbohydrates, and/or lipids.

combinations of proteins, carbohydrates, and/or lipids.

Restriction isA) 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.

C) a general host mechanism to prevent the invasion of foreign nucleic acid.

The discovery of retroviruses changed our understanding ofA) gene structure and organization.B) the flow of genetic information.C) protein synthesis.D) infectious particles.

B) the flow of genetic information.

12) Based on your knowledge of cellular and viral processes, which of the following would be(an) appropriate target(s) for antiviral drugs?A) integrasesB) aminoacyl-tRNA synthetasesC) ribosomesD) aminoacyl-tRNA synthetases and ribosomes

integrases

13) Bacteriophages' genomes are typically composed ofA) single-stranded RNA.B) single-stranded DNA.C) double-stranded RNA.D) double-stranded DNA.

double-stranded DNA.

A virus that kills its host is said to beA) lytic or virulent.B) temperate.C) lysogenic.D) virulent or lysogenic, but not temperate.

lytic or virulent.

Which of the following enzymes would you expect to find in the virion of a retrovirus, butNOT in a bacteriophage?A) lysozymeB) methylaseC) restriction enzymesD) reverse transcriptase

reverse transcriptase

The packaging mechanism of T4 DNA involves cutting of DNA fromA) linear genetic elements.B) circular genetic elements.C) DNA concatemers.D) its host cells.

C) DNA concatemers.

A prophage replicatesA) 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.

along with its host while the lytic genes are not expressed.

The virus repressor proteinA) 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.

controls both the lytic genes on the prophage and prevents an incoming virus of the sametype.

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.

Lambda is a temperate phage that replicates its double-stranded DNA genome with a rollingcircle mechanism.

Retroviruses are medically important viruses becauseA) 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.

they include viruses that cause cancer and AIDS.

The primer for retrovirus reverse transcription is a specificA) tRNA encoded by the cell.B) tRNA encoded by the virus.C) nuclear tRNA.D) nuclear tDNA.

tRNA encoded by the cell.

Rolling circle replication of the lambda genome differs from replication of a bacterialchromosome 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.

bidirectional replication forks are not formed.

23) The consequence of an infection by a temperate bacteriophage is that the bacterial cellA) 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.

may lyse before it divides or may continue to divide and replicate both the virus and the cell.

When packaged in the virion, the complete complex of nucleic acid and protein is known asthe virusA) capsid.B) concatemer.C) nucleocapsid.D) envelope.

C) nucleocapsid.

Which of the following are the hosts for most enveloped viruses?A) BacteriaB) animalsC) ArchaeaD) fungi

animals

Bacteriophage have a ________ complex structure than animal viruses, because ________.A) more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cellsB) less / the bacteriophage does not have to penetrate the nucleusC) more / the bacteriophage must penetrate the peptidoglycan cell wallD) less / there prokaryotic cells have a simple structure compared to eukaryotic cells

more / the bacteriophage must penetrate the peptidoglycan cell wall

What genome composition makes viruses most susceptible to destruction by prokaryoticrestriction endonucleases?A) dsDNAB) ssDNAC) dsRNAD) ssRNA

dsDNA

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.

infection.

29) The term "phage" is generally reserved for the viruses that infectA) animals.B) plants.C) bacteria.D) multiple species.

bacteria.

The size and shape of viral particles is largely governed by the size and packaging of theviralA) envelope.B) enzymes.C) prophage.D) genome.

D) genome.

You are attempting to mutate lambda to affect whether lysis or lysogeny occurs after lambdainfection. Which mutation would INCREASE the chances of LYSOGENY over lysis?A) deletion or inactivation of the cI geneB) deletion or inactivation of the cro geneC) overexpression of the cro geneD) deletion of both the cro and cI genes

deletion or inactivation of the cro gene

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 genesC) host's cell membrane / host's genesD) virion / host's genes

host's cell membrane / viral genes

Virions infecting some bacteria possess the enzyme ________ that makes a small hole in thebacterial cell wall, allowing the viral nucleic acid to enter.A) peptidoglycanaseB) infectaseC) lysozymeD) nuclease

lysozyme

The use of ________ is the easiest and most effective way of studying many animal andplant viruses.A) bacterial culturesB) tissue or cell cultureC) live hostsD) prophages

tissue or cell culture

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 sequencesB) plaquesC) prophagesD) colonies

B) plaques

36) T4 genes are transcribed by host RNA polymerase, yet the transcription of T4 genes iscarefully 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.

B) Early and middle T4 genes encode for proteins that modify the activity of sigma factors andhost RNA polymerase to regulate the expression of T4 genes.

The T4 phage protects its DNA from host restriction endonucleases byA) 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.

glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.

In E. coli, the adenine in the sequence GATC is methylated by the Dam enzyme. In the samecells 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.

The enzymes protect E. coli from infection by preferentially degrading viral or otherexogenous DNA that is not methylated.

39) Which of the following samples would contain the MOST genetic diversity?A) viral metagenomes from the oceanB) bacterial metagenomes from the oceanC) microbial eukaryotic metagenomes from the oceanD) viral metagenomes from human red blood cells

viral metagenomes from the ocean

Viral proteins are categorized as early, middle, and late. Early proteins typically arenecessary forA) 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.

production of viral mRNA and copying the viral genome.

A cell that allows the complete replication cycle of a virus to take place is said to be aA) permissive host.B) viral cell.C) dead cell.D) lytic cell.

A) permissive host.

In a natural population of diverse slow-growing prokaryotic cells, what type of viruses wouldyou expect to be most common?A) lytic bacteriophagesB) enveloped virusesC) icosahedral virusesD) temperate bacteriophages

lytic bacteriophages

How do bacteriophage influence bacterial evolution?A) Bacteriophage cause cleavage and rearrangement of bacterial genomes, thus accelerating bacterial evolution.B) Bacteriophage lyse mutated bacterial cells, thus preventing them from replicating and passing on their genetic information.C) Bacteriophage transfer genetic information between bacterial cells through transduction, thus increasing the genetic diversity of bacterial populations.D) Bacteriophage decrease the size of bacterial populations and thus decreasing genetic diversity and slowing down bacterial evolution.

Bacteriophage transfer genetic information between bacterial cells through transduction, thusincreasing the genetic diversity of bacterial populations.

What would be the consequence of deleting the late T4 genes?A) The T4 genome would not be copied.B) T4 mRNA would not be produced.C) T4 capsid proteins would not be made.D) ATP would not be produced and the T4 genome would not be packaged into the capsid.

C) T4 capsid proteins would not be made.

Whether lambda phage undergoes the lytic or lysogenic cycle is dependent on theaccumulation ofA) Cro protein.B) viral genomes.C) cI protein.D) methylated DNA.

C) cI protein.

You isolate a purify a bacteriophage that can replicate in E. coli. Through chemical analysesyou determine that the only nucleic acid present is RNA. You isolate the RNA and put it in a test tube with all of the necessary proteins and RNAs for translation. The RNA is translated and new infectious virions are made. What does this tell you about the bacteriophage?A) The RNA genome is of the plus sense.B) The RNA genome is of the plus sense and RNA replicase is present in the viral capsid.C) The new bacteriophage is a retrovirus.D) RNA replicase is present in the viral capsid.

The RNA genome is of the plus sense and RNA replicase is present in the viral capsid.

For bacteriophages and animal viruses ________ is the step in the viral life cycle thatdetermines host cell or tissue specificity.A) attachmentB) penetrationC) synthesisD) assembly

A) attachment

48) What are the consequences of a viral infection of an animal cell?A) rapid lysis or latent infectionsB) lysogeny followed by eventual lysisC) lysis or lysogenyD) Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer.

Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer.

In viruses, genetic information flows from ________ to ________.A) RNA / virionB) nucleic acid / proteinC) capsid / virionD) DNA / protein

nucleic acid / protein

The concentration of infectious plaque forming units (pfu) per volume of fluid is known asA) infectivity.B) virulence.C) titer.D) fluid infectivity.

C) titer.

The growth of viruses in a culture is described as a one-step growth curve, becauseA) virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.B) there is only one step in the viral life cycle which leads to only one replicative cycle in a culture.C) assembly and release actually occur in one step.D) the eclipse phase prevents the plating and enumeration of virions although new virions are produced at a steady rate during the eclipse phase.

virion numbers show no increase during intracellular replication and can only be countedafter the virions burst from the host cell.

Viruses can confer additional properties on their host cells, which can in turn be inherited.

TRUE

Viruses have both an intracellular and an extracellular form.

TRUE

Viruses can redirect host metabolic functions.

TRUE

Most of the genetic diversity on earth resides in viral genomes.

TRUE

There is at least one known virus whose genome is actually larger than a cellular genome.

Answer: TRUE

Some viruses possess icosahedral heads and helical tails.

TRUE

In the first few minutes after host cell infection, the virus undergoes an eclipse.

Answer: TRUE

Penetration requires that the entire virus is inserted within the host.

Answer: FALSE

RNA viruses encode host restriction systems designed to destroy host DNA.

FALSE

Tailed bacterial viruses can be used as genetic engineering tools.

TRUE

Although T4 encodes over 250 proteins, it does not encode its own RNA polymerase.

Answer: TRUE

Temperate viruses can enter into either a lytic or lysogenic cycle.

TRUE

Lysogeny is unique to bacteriophages; similar relationships have not been found among theanimal viruses.

FALSE

14) A temperate virus does not exist as a virus particle inside the host cell.

TRUE

15) The virus repressor protein provides immunity to infection by the same type of virus.

TRUE

A lytic infection results in death of the host cell.

TRUE

An RNA genome itself serves as mRNA in negative-stranded RNA viruses.

FALSE

The latent phase in the viral growth curve and the lag phase of the bacterial growth curve areequivalent and represent the time it takes for the virus or bacterium to adapt to the culture conditions and begin growing.

Answer: FALSE

RNA replicase is found in ALL viruses to allow the replication and transcription of viralRNA instead of host RNA.

FALSE

Which type of viruses generally has the smallest genome?A) bacteriophageB) DNA virusesC) RNA virusesD) viroids

RNA viruses

2) The Baltimore Scheme to classify viruses contains a total of ________ groups based on ________.A) four / genome compositionB) four / genome composition and transcription mechanismC) seven / genome composition D) seven / genome composition and transcription mechanism

seven / genome composition and transcription mechanism

Early and late viral proteins are classified according to their relativeA) evolutionary appearance in virus genomes.B) stability during infection.C) time of synthesis following host infection.D) transmission into virions.

C) time of synthesis following host infection.

4) Which type of viruses can be directly used for translation?A) dsRNAB) negative ssRNAC) positive ssRNAD) retroviruses

positive ssRNA

5) If the hypothesis stating viruses evolved prior to living organisms on Earth is true, the first type of viruses in the world were likelyA) bacteriophage.B) DNA viruses.C) retroviruses.D) RNA viruses.

RNA viruses.

The filamentous DNA phages are unusual, because theyA) are released from the host without the host being lysed.B) have linear genomes.C) replicate without a host.D) are released from the host without being lysed and have linear genomes.

are released from the host without the host being lysed.

How could overlapping genes in a positive ssDNA virus genome be predicted?A) Convert the positive ssDNA into its complementary ssDNA and search for genes in the negative ssDNA strand for sequences used in more than one predicted gene.B) Directly search the three frames of the positive ssDNA for genes that have sequences where more than one gene is predicted.C) Convert the positive ssDNA into negative ssDNA and search all six possible frames for genes that use part of the same sequence.D) Convert the positive ssDNA into its complementary ssDNA and search for genes in the negative ssDNA strand that also share a complementary gene in the positive strand.

Directly search the three frames of the positive ssDNA for genes that have sequences wheremore than one gene is predicted.

How are T7 genes transcribed?A) Host RNA polymerase is modified to recognize the T7 promoter.B) Host RNA polymerase directly translates the T7 genes.C) T7 has its own RNA polymerase, which is packaged in its capsid and injected into the host during infection to transcribe T7 genes.D) T7 has its own RNA polymerase, which must first be synthesized by the host.

T7 has its own RNA polymerase, which must first be synthesized by the host.

In T7, the proteins that inhibit the host restriction system are synthesizedA) before the entire T7 genome enters the cell.B) while the T7 genome is entering the cell but before it enters the nucleus.C) after the T7 genome is completely within the host cytoplasm.D) in response to the T7 genome binding to the host chromosome.

A) before the entire T7 genome enters the cell.

A concatemer is aA) combination of two or more repeated nucleotide sequences covalently linked together.B) complex of RNA-specific polymerases found only in bacteriophages.C) linker molecule that allows several phages to infect one host.D) polymeric protein.

combination of two or more repeated nucleotide sequences covalently linked together.

The phage MuA) has a circular genome.B) repairs mutations in the host genome.C) replicates by transposition.D) has a circular genome, repairs host genome mutations, and can replicate by transposition.

replicates by transposition.

Mu is a ________ virus with a ________ tail.A) ssRNA / filamentousB) dsRNA / helicalC) ssDNA / filamentousD) dsDNA / helical

dsDNA / helical

13) Integration of Mu DNA into the host genome is essential forA) lytic growth.B) lysogenic growth.C) both lytic and lysogenic growth.D) neither lytic nor lysogenic growth.

both lytic and lysogenic growth.

Most known plant viruses have ________-strand RNA genomes, because small genomes________.A) negative / facilitate cell-to-cell transferB) positive / facilitate cell-to-cell transferC) negative / interact more readily with host DNAD) positive / interact more readily with host DNA

B) positive / facilitate cell-to-cell transfer

Which feature, if changed, would NOT abolish M13's utility as a cloning vector?A) ssDNA genome becoming a dsDNA genomeB) loss of genes that make coat proteinsC) replacing the segment of non-coding DNA in its genome with an indispensible geneD) switch from lysogenic to lytic lifestyle

ssDNA genome becoming a dsDNA genome

Of the phage listed below, which creates mutations in its host genome via transposition?A) lambdaB) M13C) MuD) T7

C) Mu

Unusually shaped viruses, such as lemon-shaped and spindle-shaped, have recently beendiscovered inA) Archaea.B) Bacteria.C) Archaea and Bacteria.D) Eukarya.

A) Archaea.

Reoviruses contain ________ genomes, and their replication occurs within the host's________.A) ssDNA / nucleusB) dsDNA / nucleusC) ssRNA / cytoplasmD) dsRNA / cytoplasm

dsRNA / cytoplasm

What will happen if the Mu repressor is not synthesized?A) Genome replication will not be able to occur.B) It will lyse its host.C) Mu will improperly synthesize its capsid.D) Transposition will not be possible.

It will lyse its host.

Viruses that infect the hyperthermophilic Archaea tend to contain genomes that arecomposed ofA) ssDNA.B) dsDNA.C) ssRNA.D) dsRNA.

dsDNA.

Spindle-shaped viruses have been shown to infect onlyA) Eukarya.B) Bacteria.C) Archaea.D) plants.

C) Archaea.

In designing a drug to inhibit pox viruses, the compound should localize in the host's________ to be MOST effective.A) nucleusB) endoplasmic reticulumC) cytoplasmD) Golgi complex

C) cytoplasm

The unconventional dsDNA genome replication mechanism where no lagging strand exists isa hallmark of which group of viruses?A) adenovirusesB) coronavirusesC) herpes virusesD) pox viruses

adenoviruses

The hepadnavirus DNA polymerase acts as which of the following?A) DNA polymeraseB) reverse transcriptaseC) protein primer for synthesis of a strand of DNAD) DNA polymerase, reverse transcriptase, and protein primer for DNA synthesis

D) DNA polymerase, reverse transcriptase, and protein primer for DNA synthesis

Gene therapy viruses are usually constructed from which type of virus?A) adenovirusesB) cytomegalovirusesC) polyomavirusesD) poxviruses

A) adenoviruses

26) Blocking polyomavirus SV40's ability to integrate its genome into host cells wouldA) avoid cancer development from the virus.B) increase the rate of transformation.C) increase the latent period of SV40.D) switch SV40 into a lytic lifecycle which would be especially harmful to the host cells.

A) avoid cancer development from the virus.

Herpesviruses can cause all of the following diseases in humans EXCEPTA) cancer.B) chicken pox.C) cold sores.D) spongiform encephalopathy.

spongiform encephalopathy.

What is unusual about phage MS2 infection of Escherichia coli?A) All proteins are synthesized simultaneously during infection so there are no early and late proteins.B) It attaches to the host's pilus rather than the cell's surface.C) It enters through a host cell porin.D) More than one MS2 phage can be present in an individual E. coli cell.

It attaches to the host's pilus rather than the cell's surface.

Based on its function, which type(s) of viruses likely contain(s) a gene encoding for RNAreplicase?A) dsDNA and ssDNA virusesB) positive ssRNA virusesC) positive and negative ssRNA virusesD) ssRNA and ssDNA viruses

positive and negative ssRNA viruses

Polyproteins made from human viruses such as poliovirus must be ________ in order toyield the required functional units of the virus.A) able to interact with VPg proteinsB) chemically modified with either glycolation or methylationC) post-translationally cleavedD) properly folded into secondary and tertiary structures

post-translationally cleaved

What is the purpose of synthesizing a negative strand RNA in positive stranded ssRNAviruses?A) enable rolling circle amplification of the genome, which requires both strands of RNAB) enable transcription of genes occurring on both the negative and positive strands of the genome, such as overlapping genesC) proofreading of the genome to minimize mutations generated by the polymerase being passed onto virion progenyD) to serve as the complementary template sequence in genome amplification of the positive strand

to serve as the complementary template sequence in genome amplification of the positivestrand

Among the largest RNA genome viruses are ________ which contain a ________ genome.A) coronaviruses / dsRNAB) coronaviruses / positive ssRNAC) polioviruses / dsRNAD) polioviruses / positive ssRNA

coronaviruses / positive ssRNA

As a consequence of the immune system in humans recognizing dsRNA as foreign,A) dsRNA viruses rarely infect humans.B) dsRNA viruses quickly transcribe their genes into mRNA which is insensitive to immune responses.C) genomes of RNA viruses are often chemically modified to avoid recognition by human immune cells.D) the genomes of dsRNA viruses must avoid human immune cells during infection, including replicating their genomes within their own nucleocapsids.

the genomes of dsRNA viruses must avoid human immune cells during infection, includingreplicating their genomes within their own nucleocapsids.

To promote the translational activity of ribosomes in human cells for synthesizing viralproteins during viral infection, virusesA) chemically modify (e.g., cap and methylate) the transcripts.B) keep a ribosome binding site specific to human ribosomes on their genome.C) maintain introns and sometimes extrons in their genomes to appear as eukaryotic mRNA.D) only adhere to and infect metabolically active host cells where protein synthesis is high.

chemically modify (e.g., cap and methylate) the transcripts.

35) The family of reoviruses contain dsRNA genomes that replicate from the template of________ which makes it a ________ replication process.A) only the positive ssRNA strand / conservativeB) only the positive ssRNA strand / semiconservativeC) both RNA strands /conservativeD) both RNA strands / semiconservative

A) only the positive ssRNA strand / conservative

Identifying proteases being essential for replication of a virus would suggest the virusA) lyses its host following genome replication.B) contains at least one polyprotein.C) has a single-stranded RNA genome.D) uses at least one set of overlapping genes.

contains at least one polyprotein.

A drug designed to inhibit reverse transcriptase activity would targetA) coronaviruses and rhabdoviruses.B) hepadnaviruses and retroviruses.C) retroviruses.D) viruses with RNA genomes.

hepadnaviruses and retroviruses.

38) In contrast to positive ssRNA viruses such as coronaviruses and polioviruses, the genome ofretrovirusesA) lacks genes encoding for tRNA primers.B) must first integrate into the host's genome before transcription.C) is negative ssRNA.D) lacks ribonuclease activity.

must first integrate into the host's genome before transcription.

Proteins made by a ribosome reading through a transcript's stop codon without their owndiscrete ribosome binding sitesA) are thought to be a primitive mechanism to avoid host defenses.B) appear most abundant in archaeal viruses and relatively uncommon in bacteriophage.C) suggest a relatively low level of protein product is essential for the virus due to its rare frequency.D) create opportunities for viruses to make different capsid proteins.

suggest a relatively low level of protein product is essential for the virus due to its rarefrequency.

Viruses are known to infect Bacteria, but no virus has yet been found that infects Archaea.

FALSE

To date, no virus that infects Archaea is known to have an RNA genome.

FALSE

Genomics analysis of recently isolated viruses indicate some viruses contain larger genomesthan the some bacterial genomes.

TRUE

The Baltimore classification scheme is a useful way to categorize viruses based on their hostinfectivity.

Answer: FALSE

Viruses that contain positive-strand genomes are incompatible to share genetic elements otherpositive-strand genomes.

FALSE

Varied transcription mechanisms distinguish the different DNA virus Baltimore classes,whereas varied translational mechanisms distinguish RNA viruses.

FALSE

Despite viruses require a living host's metabolism to replicate, it remains unclear whetherviruses existed before living cells.

Answer: TRUE

One hypothesis on the origin of DNA points to RNA viruses evolving a modified nucleotidethat is insensitive to ribonucleases.

TRUE

Due to the genetic diversity of viruses and their lack of ribosomal RNA, nucleotide-basedphylogeny studies are not applicable to virology.

Answer: FALSE

Bacteriophage that have single-stranded genomes are specialized to minimize energyrequirements because just one strand is necessary for replication.

Answer: FALSE

The diversity of genome type and the overall number of bacteriophage that infectEscherichia coli is numerous, but many other bacterial taxa that thrive in the environment are likely infected by a variety of phage as well.

Answer: TRUE

Nonfilamentous bacteriophage often can escape its host without lysing, whereas filamentousphage normally induce cell lysis once replicated inside their host.

Answer: FALSE

By nature of its infectivity, M13 phage can be used in the laboratory to continually propagatea particular DNA sequence inside of Escherichia coli by simply culturing infected E. coli in LB.

TRUE

Knowing the genome of Mu bacteriophage now enables researchers to locate where itincorporates into bacterial genomes.

TRUE

Some virus shapes that infect members of Archaea are unique from other viruses that infecteukaryotes and bacteria.

TRUE

Most archaeal viruses identified appear to have DNA genomes.

TRUE

Many human-infecting viruses that illicit a strong immune response cause additional harmfuleffects on humans, so the discovery of a virus that can induce an immune response but not cause harm made it attractive for vaccine development.

TRUE

Due to their indispensible role for copying its genome, an intracellular host protease thatattacks the adenoviral protein ends would likely result in halting its replication.

TRUE

A negative-stranded RNA virus produces a complete positive-stranded RNA virus that servesas template DNA for other proteins in order to replicate the complete negative-stranded RNA genome.

FALSE

A bacteriophage that lacks its proteinaceous capsid structure is also called a viroid.

FALSE