Bio 319- Chapter 8

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

A) permissive host.

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.

A) tRNA encoded by the cell.

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

A) viral metagenomes from the ocean

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

C) lysozyme

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.

A) lytic or virulent.

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.

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.

A) are metabolically inert.

For bacteriophages and animal viruses ________ is the step in the viral life cycle that determines host cell or tissue specificity. A) attachment B) penetration C) synthesis D) assembly

A) attachment

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.

A) bidirectional replication forks are not formed.

What genome composition makes viruses most susceptible to destruction by prokaryotic restriction endonucleases? A) dsDNA B) ssDNA C) dsRNA D) ssRNA

A) dsDNA

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.

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

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

A) host's cell membrane / viral genes

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.

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

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

A) integrases

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

A) intracellularly.

In a natural population of diverse slow-growing prokaryotic cells, what type of viruses would you expect to be most common? A) lytic bacteriophages B) enveloped viruses C) icosahedral viruses D) temperate bacteriophages

A) lytic bacteriophages

The growth of viruses in a culture is described as a one-step growth curve, because A) 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.

A) virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.

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.

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.

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.

B) Many viruses contain their own nucleic acid polymerases.

You isolate a purify a bacteriophage that can replicate in E. coli. Through chemical analyses you 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.

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

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.

B) along with its host while the lytic genes are not expressed

Which of the following are the hosts for most enveloped viruses? A) Bacteria B) animals C) Archaea D) fungi

B) animals

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

B) deletion or inactivation of the cro gene

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.

B) infection.

In viruses, genetic information flows from ________ to ________. A) RNA / virion B) nucleic acid / protein C) capsid / virion D) DNA / protein

B) nucleic acid / protein

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

B) plaques

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.

B) the flow of genetic information.

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

B) tissue or cell culture

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

C) lipid bilayers / glycoproteins

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.

C) Bacteriophage transfer genetic information between bacterial cells through transduction, thus increasing the genetic diversity of bacterial populations.

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.

C) DNA concatemers

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.`

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.

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

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

C) bacteria.

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

C) cI protein.

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.

C) controls both the lytic genes on the prophage and prevents an incoming virus of the same type.

`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

C) more / the bacteriophage must penetrate the peptidoglycan cell wall

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

C) nanometers.

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.

C) nucleocapsid.

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

C) titer.

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.

D) Lambda is a temperate phage that replicates its double-stranded DNA genome with a rolling circle mechanism.

What are the consequences of a viral infection of an animal cell? A) rapid lysis or latent infections B) lysogeny followed by eventual lysis C) lysis or lysogeny D) Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer

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

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.

D) The enzymes protect E. coli from infection by preferentially degrading viral or other exogenous DNA that is not methylated.

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

D) combinations of proteins, carbohydrates, and/or lipids.

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

D) double-stranded DNA.

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.

D) genome.

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.

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

`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.

D) production of viral mRNA and copying the viral genome.

Viruses infecting ________ are typically the easiest to grow in the laboratory. A) plants B) animals C) fungi D) prokaryotes

D) prokaryotes

`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

D) reverse transcriptase

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.

D) they include viruses that cause cancer and AIDS.