Chapter 10 questions

A concatemer is a A) 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.

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

The family of reoviruses contain dsRNA genomes use a ________ replication process. A) conservative B) semiconservative C) retroviral D) rolling circle

A) conservative

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

C) Archaea.

If the hypothesis stating viruses evolved prior to living organisms on Earth is TRUE, the first type of viruses in the world were likely A) bacteriophages. B) DNA viruses. C) retroviruses. D) RNA viruses.

D) RNA viruses.

T/F:A bacteriophage that lacks its proteinaceous capsid structure is also called a viroid.

F

T/F:Bacteriophages that have single-stranded genomes are specialized to minimize energy requirements because just one strand is necessary for replication.

F

T/F:Due to the genetic diversity of viruses and their lack of ribosomal RNA, nucleotide-based phylogeny studies are not applicable to virology.

F

T/F:In order to replicate its genome, a positive-strand RNA virus must produce a complete negative-strand RNA molecule that serves as the template for protein synthesis.

F

T/F:Nonfilamentous bacteriophages often can escape its host without lysing, whereas filamentous phages normally induce cell lysis once replicated inside their host.

F

T/F:Most archaeal viruses identified appear to have DNA genomes.

T

Unusually shaped viruses, such as lemon-shaped and spindle-shaped, have recently been discovered in A) Archaea. B) Bacteria. C) Archaea and Bacteria. D) Eukarya.

A) Archaea.

How do reoviruses increase the translational activity of human ribosomes so that they can rapidly produce viral proteins during infection? A) They chemically modify the RNA transcripts with methyl caps in a similar manner to normal eukaryotic RNA processing. B) They keep a ribosome binding site specific to human ribosomes on their genome. C) They have introns and sometimes extons in their genomes to make their RNA resemble eukaryotic mRNA. D) They only adhere to and infect metabolically active host cells where protein synthesis is high.

A) They chemically modify the RNA transcripts with methyl caps in a similar manner to normal eukaryotic RNA processing.

The unconventional dsDNA genome replication mechanism where no lagging strand exists is a hallmark of which group of viruses? A) adenoviruses B) coronaviruses C) herpes viruses D) pox viruses

A) adenoviruses

The filamentous DNA phages are unusual, because they A) 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.

A) are released from the host without the host being lysed.

Blocking polyomavirus SV40ʹs ability to integrate its genome into host cells would A) avoid cancer development caused by 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 caused by the virus.

In T7, the proteins that inhibit the host restriction system are synthesized A) 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.

Which feature, if changed, would NOT abolish M13ʹs utility as a cloning vector? A) ssDNA genome becoming a dsDNA genome B) loss of genes that make coat proteins C) replacing the segment of non-coding DNA in its genome with an indispensible gene D) switch from lysogenic to lytic lifestyle

A) ssDNA genome becoming a dsDNA genome

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.

B) Directly search the three frames of the positive ssDNA for genes that have sequences where more than one gene is predicted.

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 hostʹs pilus rather than the cellʹs surface. C) It enters through a host cell porin. D) More than one MS2 phage can be present in an individual E. coli cell.

B) It attaches to the hostʹs pilus rather than the cellʹs surface.

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.

B) It will lyse its host.

When two different influenza viruses infect the same cell, their segmented genomes can undergo reassortment which will result in A) antigenic drift. B) antigenic shift. C) loss of neuramidase. D) loss of hemagglutinin.

B) antigenic shift.

Identifying proteases being essential for the replication of a virus would suggest the virus A) 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.

B) contains at least one polyprotein.

Among the largest RNA genome viruses are ________ which contain a ________ genome. A) coronaviruses / dsRNA B) coronaviruses / positive ssRNA C) polioviruses / dsRNA D) polioviruses / positive ssRNA

B) coronaviruses / positive ssRNA

Viruses that infect the hyperthermophilic Archaea tend to contain genomes that are composed of A) ssDNA. B) dsDNA. C) ssRNA. D) dsRNA.

B) dsDNA.

In contrast to positive ssRNA viruses such as coronaviruses and polioviruses, the genome of retroviruses A) lacks genes encoding for tRNA primers. B) must first integrate into the hostʹs genome before transcription. C) is negative ssRNA. D) lacks ribonuclease activity.

B) must first integrate into the hostʹs genome before transcription.

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

B) retroviruses.

Which of the following conditions favors a lysogenic life cycle in bacteriophages? A) Having ssDNA. B) Having ssRNA. C) A lack of host bacteria. D) The presence of abundant hosts.

C) A lack of host bacteria.

Of the phages listed below, which creates mutations in its host genome via transposition? A) lambda B) M13 C) Mu D) T7

C) Mu

Which type of viruses generally has the smallest genome? A) bacteriophages B) DNA viruses C) RNA viruses D) viroids

C) RNA viruses

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

C) both lytic and lysogenic growth.

In designing a drug to inhibit poxvirus, the compound should localize in the hostʹs ________ to be most effective. A) nucleus B) endoplasmic reticulum C) cytoplasm D) Golgi complex

C) cytoplasm

Based on its function, which type(s) of viruses likely contain(s) a gene encoding for RNA replicase? A) dsDNA and ssDNA viruses B) positive ssRNA viruses C) positive and negative ssRNA viruses D) ssRNA and ssDNA viruses

C) positive and negative ssRNA viruses

Which type of viruses can be directly used for translation? A) dsRNA B) negative ssRNA C) positive ssRNA D) retroviruses

C) positive ssRNA

Polyproteins made from human viruses such as poliovirus must be ________ in order to yield the required functional units of the virus. A) able to interact with VPg proteins B) chemically modified with either glycolation or methylation C) post-translationally cleaved D) properly folded into secondary and tertiary structures

C) post-translationally cleaved

The phage Mu A) 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.

C) replicates by transposition.

Mu is a ________ virus with a ________ tail. A) ssRNA / filamentous B) dsRNA / helica lC) ssDNA / filamentous D) dsDNA / helical

D) dsDNA / helical

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

C) suggest a relatively low level of protein product is essential for the virus due to the rare frequency of these events.

Early and late viral proteins are classified according to their relative A) 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.

The ________ has been especially useful for genetic engineering because it is capable of triggering a substantial immune response without causing major adverse health effects. A) adenovirus B) polymyxavirus C) vaccina virus D) herpesvirus

C) vaccina virus

Reoviruses contain ________ genomes, and their replication occurs within the hostʹs ________. A) ssDNA / nucleus B) dsDNA / nucleus C) ssRNA / cytoplasm D) dsRNA / cytoplasm

D) dsRNA / cytoplasm

The hepadnavirus DNA polymerase acts as which of the following? A) DNA polymerase B) reverse transcriptase C) protein primer for synthesis of a strand of DNA D) DNA polymerase, reverse transcriptase, and protein primer for DNA synthesis

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

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.

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

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

D) seven / genome composition and transcription mechanism

Herpes viruses can cause all of the following diseases in humans EXCEPT A) cancer. B) chicken pox. C) cold sores. D) spongiform encephalopathy.

D) spongiform encephalopathy.

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.

D) the genomes of dsRNA viruses must avoid human immune cells during infection, including replicating their genomes within their own nucleocapsids

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

D) to serve as the complementary template sequence in genome amplification of the positive strand

T/F:The Baltimore classification scheme is a useful way to categorize viruses based on their host infectivity.

F

T/F:To date, there is no evidence that RNA viruses infect Archaea.

F

T/F:Varied transcription mechanisms distinguish the different DNA virus Baltimore classes, whereas varied translational mechanisms distinguish the RNA virus Baltimore classes.

F

T/F:Viroids infect only fungi.

F

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

F

T/F:Viruses that contain positive-strand genomes do not share genetic elements with other positive-strand genomes.

F

T/F:By nature of its infectivity, M13 phages can be used in the laboratory to continually propagate a particular DNA sequence inside of Escherichia coli by simply culturing infected E.

T

T/F:Despite viruses require a living hostʹs metabolism to replicate, it remains unclear whether viruses existed before living cells.

T

T/F:Due to their indispensible role for copying its genome, an intracellular host protease that attacks the adenoviral protein ends would likely result in halting its replication.

T

T/F:Genomics analysis of recently isolated viruses indicate that some viruses contain larger genomes than some bacterial genomes.

T

T/F:Knowing the genome of Mu bacteriophages now enables researchers to locate where it incorporates into bacterial genomes.

T

T/F:Many viruses that infect humans may illicit a strong immune response causing additional harmful effects, so the discovery of a virus that can induce an immune response without causing harm made it attractive for vaccine development.

T

T/F:One hypothesis on the origin of DNA points to RNA viruses evolving a modified nucleotide that is insensitive to ribonucleases.

T

T/F:Some virus shapes that infect members of Archaea are unique from other viruses that infect eukaryotes and bacteria.

T