Viruses & Prions (MasteringMicro)

(T/F) All persistent viral infections occur when the virus integrates into the host cell DNA to form a provirus.

false

(T/F) Antiviral drugs exist that target all stages of viral replication except the production of viral nucleic acids.

false

(T/F) Both viruses and prokaryotes reproduce by binary fission.

false

(T/F) Like bacteriophage, when an animal cell virus enters a host cell, only the genome enters while the capsid remains outside the cell.

false

(T/F) Naked viruses usually exit the animal host cell by budding while enveloped viruses exit by lysis.

false

(T/F) The shape of a virus may be determined by either its capsid or its envelope.

false

Which of the following are ways that viruses differ from prokaryotes and eukaryotes? Select all true statements. Unlike prokaryotes and eukaryotes... a) viruses are incapable of replicating independently from a host cell. b) viruses do not have genomes. c) viruses are classified as acellular particles. d) viruses are not considered alive.

Unlike prokaryotes and eukaryotes... a) viruses are incapable of replicating independently from a host cell. c) viruses are classified as acellular particles. d) viruses are not considered alive.

A young patient who underwent surgical placement of depth electrodes for epilepsy treatment contracted a prion disease. Cortical electrode probes are known to be reused in patients. Based on this information, which of the following prion diseases did the young patient most likely contract? a) Iatrogenic Creutzfeldt-Jakob Disease b) Variant Creutzfeldt-Jakob Disease c) Inherited Creutzfeldt-Jakob Disease d) Sporadic Creutzfeldt-Jakob Disease

a) Iatrogenic Creutzfeldt-Jakob Disease

Which replicative step(s) do animal viruses and bacteriophages have in common? Select all true statements. a) Penetration b) Uncoating c) Assembly d) Attachment

a) Penetration c) Assembly d) Attachment

Which of the following observations supports the statement that cytomegalovirus (CMV) has a remarkably broad tropism? a) Infection with CMV can occur through various portals of entry, including genitourinary, vertical transmission, and direct contact with infectious tissues, secretions, or excretions. b) CMV can infect connective tissue cells and parenchymal cells of virtually any organ. c) CMV is a universally distributed pathogen, with approximately 40-100% of the world's population having shown immunological evidence of infection. d) Different strains of CMV have been shown to infect humans, rodents, and rhesus monkeys.

b) CMV can infect connective tissue cells and parenchymal cells of virtually any organ.

Which of the following is a key difference between lytic and lysogenic bacteriophage replication cycles? a) The lytic replication cycle ends with host cell lysis and release of newly formed bacteriophage particles, whereas lysogenic replication leads to prophage formation. b) Lysogenic bacteriophages release via host cell lysis, whereas lytic bacteriophages bud off from the host cell membrane. c) Lytic replication requires an uncoating step, whereas in lysogenic replication, the bacteriophage's nucleic acid is directly injected into the host cell. d) Whereas lytic replication enables the infection of several hosts, lysogenic replication only allows for infection of a single host cell.

a) The lytic replication cycle ends with host cell lysis and release of newly formed bacteriophage particles, whereas lysogenic replication leads to prophage formation.

You are studying an unknown virus that does not perform transcription to make viral proteins. Which of the following characteristics must also be true for this unknown virus? a) The virus has a positive, sense-stranded RNA genome. b) The virus has a double-stranded RNA genome. c) The viral genome must encode reverse transcriptase. d) The viral genome must encode RNA-dependent RNA polymerases.

a) The virus has a positive, sense-stranded RNA genome.

Chlamydia trachomatis is an obligate intracellular bacterium that causes the sexually transmitted disease chlamydia. When this bacterium was first discovered, it was classified as a virus. However, it was later re-classified as a bacterium. Which of the following is the most likely reason why C. trachomatis was reclassified as a living bacterial cell as opposed to a nonliving viral particle? a) capable of performing metabolic processes. b) lacks membrane-bound organelles, such as a nucleus. c) has a genome consisting of double-stranded DNA. d) is visible with a compound light microscope.

a) capable of performing metabolic processes

The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by __________________________. a) the spikes that protrude from its viral envelope b) the helical shape of its viral capsid c) the type of nucleic acid used for its viral genome (single-stranded, antisense RNA) d) the segmented nature of its viral genome

a) the spikes that protrude from its viral envelope

Which property is NOT used to classify viruses? a) tissue types infected b) genome architecture c) type of nucleic acid present d) presence or absence of an envelope e) capsid symmetry

a) tissue types infected

Which of the following genome types has been observed in viruses? Select all true statements. a) Protein-based b) Double-stranded RNA c) Single-stranded DNA d) Single-stranded RNA

b) Double-stranded RNA c) Single-stranded DNA d) Single-stranded RNA

HIV, the virus which causes AIDS, interacts with two receptors on the host cell membrane: CD4 and CCR5. A small percentage of individuals have a genetic mutation which causes their cells to lack CCR5. These individuals will never develop AIDS nor are they able to pass HIV on to others. Which part of viral replication is being blocked by the lack of a receptor? a) The virus components cannot be assembled into new virions. b) HIV cannot attach to the host cell without the proper membrane receptor. c) The host cell enzymes are unable to replicate the HIV genome. d) Endocytosis is being prevented. e) Newly assembled virions cannot be released from the host cell.

b) HIV cannot attach to the host cell without the proper membrane receptor.

Which statement is NOT true about chronic persistent viral infections? a) Small numbers of virions may be produced and released from host cells during the quiet periods. b) May involve periods of flare-up where the virus is actively replicating alternating with periods of dormancy. c) A period of quiet infection where the host is asymptomatic is followed by a period of active viral replication. d) The immune system fails to clear the infection. e) May involve integration of the virus into the host cell DNA to form a provirus.

b) May involve periods of flare-up where the virus is actively replicating alternating with periods of dormancy.

Which stage of animal virus replication may be blocked by a drug that binds with the viral spike? a) replication b) attachment c) assembly d) penetration e) uncoating

b) attachment

Which stage of animal virus replication will not be different between naked viruses and enveloped viruses? a) uncoating b) replication c) assembly d) penetration e) release

b) replication

Oncogenic viruses... a) suppress the host immune system. b) stimulate uncontrolled host cell division. c) are never RNA viruses. d) increase host cell responsiveness to death signals. e) always integrate into the host cell DNA.

b) stimulate uncontrolled host cell division.

Which description of antigenic drift and antigenic shift in the influenza virus is incorrectly matched? a) Antigenic drift: A host vaccinated against an influenza strain before antigenic drift may lack effective immunity and be susceptible to infection. b) Antigenic shift: May result in a pandemic outbreak due to widespread lack of immunity. c) Antigenic drift: Often involves reassortment of viral strains in an animal host followed by a "species jump" to humans. d) Antigenic shift: Often leads to viral strains with new features such as increased infectivity or expanded host range. e) Antigenic drift: Spontaneous mutation leads to a minor change in HA or NA spikes.

c) Antigenic drift: Often involves reassortment of viral strains in an animal host followed by a "species jump" to humans.

An elderly patient who contracted chickenpox as a child now has shingles as an adult. You explain to your patient that both diseases are caused by the same virus, which lays dormant in the body prior to reactivation. Based on this information, choose the true statement. a) Viral replication occurs as a steady, logarithmic increase over time. b) Your patient's infection is best characterized as an acute, non-persistent infection. c) During dormant periods, the virus exists episomally inside of infected host cells. d) Infected host cells will carry a provirus until sufficient viral load has been reached.

c) During dormant periods, the virus exists episomally inside of infected host cells.

You observe that a novel virus penetrates the host cell through membrane fusion. Which of the following statements must also be true regarding this virus and its replicative cycle? a) The virus does not undergo uncoating. b) The virus undergoes lysogenic replication. c) The virus releases from host cells by budding. d) Replication occurs in the nucleus of the host cell.

c) The virus releases from host cells by budding.

Viruses are considered to be non-living pathogens for which reason? a) their extremely small size b) their unique type of cells and their lack of metabolic processes c) their lack of metabolic processes d) their ability to synthesize only some of their own components e) their unique type of cells

c) their lack of metabolic processes

A newly-discovered double-stranded RNA virus which infects animal cells is found to contain a unique enzyme which synthesizes double-stranded RNA using an RNA template. Which of the following statements is likely to be true? a) The enzyme probably came from the host animal cell and is coded for by a gene in the host cell. b) The enzyme probably came from the host animal cell. c) This enzyme would not be a good antiviral drug target as the host cell likely has a similar enzyme which could be affected by such a drug. d) The virus must bring this enzyme into the host cell as synthesizing RNA from an RNA template does not happen in animal cells. e) This enzyme is coded for by a gene in the host cell.

d) The virus must bring this enzyme into the host cell as synthesizing RNA from an RNA template does not happen in animal cells.

In the Spring of 2009, a novel H1N1 virus emerged that had a new combination of genes from pigs, humans, and birds. As a result, the virus spread quickly, resulting in a swine flu pandemic. Which of the following concepts explains why the outbreak occurred? a) Narrow tropism b) Antigenic drift c) Attenuation d) Antigenic shift

d) antigenic shift

Compared to both prokaryotic and eukaryotic cells, viruses... a) have similar metabolic processes. b) lack genetic material. c) lack proteins. d) are generally smaller. e) are not filterable.

d) are generally smaller

Viruses which infect many different tissues types are said to have a(n) a) indeterminate host range. b) broad host range. c) narrow tropism. d) broad tropism. e) narrow host range.

d) broad tropism

When a virus has an envelope, a) it is always an RNA-containing virus. b) it may escape its host cell either by budding or by lysis. c) it is always a bacteriophage. d) it likely escapes its host cell by budding. e) it likely escapes its host cell by lysis.

d) it likely escapes its host cell by budding

All viruses must use their genome to produce ________, which is then used by the host cell to produce ________. a) DNA; mRNA b) proteins; mRNA c) DNA; proteins d) mRNA; proteins e) proteins; DNA

d) mRNA; proteins

Which is NOT a cancer linked to a specific virus? a) cervical cancer b) Kaposi sarcoma c) liver cancer d) skin cancer e) adult T-cell leukemia

d) skin cancer

Which statement is NOT true about the virus capsid? a) The capsid functions as a package for the viral genetic material. b) The capsid is made of one or more types of protein subunits. c) The capsid determines the shape of the virus. d) Both bacteriophage and animal viruses have capsids. e) Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs

e) Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs

Animal viruses can be grown in all of the following EXCEPT a) embryonated eggs. b) HeLa cells. c) tissue culture. d) live animal hosts. e) E. coli cells.

e) E. coli cells

Which genomic arrangement has NOT been found in viruses? a) double-stranded DNA b) single-stranded RNA c) double-stranded RNA d) single-stranded DNA e) a combination of DNA and RNA in the same virus

e) a combination of DNA and RNA in the same virus

Viral spikes... a) show specificity in binding to particular structures on the host cell. b) allow the virus to attach and enter host cells but do not show specificity for a particular structure on the host cell. c) may be a target for the host immune system. d) allow the virus to attach and enter host cells. e) allow the virus to attach and enter host cells, may be a target for the host immune system, and show specificity in binding to particular structures on the host cell.

e) allow the virus to attach and enter host cells, may be a target for the host immune system, and show specificity in binding to particular structures on the host cell.

The key event that occurs during lysogenic replication of bacteriophage that does not occur during lytic replication is... a) assembly of new phage by packing viral genomes into capsids. b) penetration of the phage DNA into the host cell. c) attachment of the phage to specific proteins in the bacterial cell. d) release of mature viral particles by lysis of the bacterial cell. e) integration of the phage DNA into the host cell DNA.

e) integration of the phage DNA into the host cell DNA.

Which of the following prion diseases may be acquired by eating beef contaminated with a cattle prion? a) Gerstmann-Straussler-Schienker syndrome b) iatrogenic CJD c) sporadic CJD d) inherited CJD e) variant CJD

e) variant CJD

(T/F) The number of species that a specific virus infects is called its host range while the types of tissues that the virus infects is called tropism.

true