Microbiology: Chapter 6

Which of the following would be the best general description of a "virus?" a) Viruses are cells without a nucleus or other membrane-bound organelles. b) Viruses are acellular infectious agents. c) Viruses are cells with a nucleus and membrane-bound organelles. d) Viruses are acellular infectious agents with DNA genomes.

b) Viruses are acellular infectious agents.

Which of the following suffixes would be used to describe a viral family? a) -virus b) -virinae c) -virales d) -viridae

d) -viridae

Viruses are considered to be non-living pathogens for which reason?

Their lack of metabolic processes.

Which stage of animal virus replication may be blocked by a drug that binds with the viral spike?

attachment

The protein shell that packages and protects the genome and also accounts for the bulk of a virion's mass is called a _________.

capsid

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) Sporadic Creutzfeldt-Jakob Disease b) Inherited Creutzfeldt-Jakob Disease c) Variant Creutzfeldt-Jakob Disease d) Iatrogenic Creutzfeldt-Jakob Disease

d) Iatrogenic Creutzfeldt-Jakob Disease

Oncogenic viruses:

stimulate uncontrolled host cell division.

The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by __________________________.

the spikes that protrude from its viral envelope.

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?

Antigenic shift

Bacteriophages use different mechanisms for host cell infection and viral replication. During the lytic replication pathway, bacteriophages infect the host bacterial cells and immediately build new virions. During which of the key steps is the genome packed into capsid and phage structures put together?

Assembly

You are comparing the size of different viruses. You are specifically interested in the size of the following viruses: Ebola virus, Poliovirus, Rhinivirus, and Pithovirus. Which of these viruses would be the smallest, and which the largest?

Poliovirus is the smallest; Pithovirus the largest.

Cells can only contain which of the following types of genomes? a) A double-stranded DNA genome b) A single-stranded DNA genome c) A double-stranded RNA genome d) A single-stranded RNA genome

a) A double-stranded DNA genome

Which of the following is an example of phage conversion? a) Lambda phages can use either the lytic cycle or lysogenic pathway for replication. b) Infection of Streptococcus pyogenes with T12 phage enables the bacteria to produce erythrogenic toxins, allowing it to cause scarlet fever. c) Despite a single infection, ultimately multiple host cells will carry the bacteriophage genome during the lysogenic replication cycle. d) Following injection of viral nucleic acid into a host cell, the genetic material is incorporated into the host genome.

b) Infection of Streptococcus pyogenes with T12 phage enables the bacteria to produce erythrogenic toxins, allowing it to cause scarlet fever.

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

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

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

e) tissue types infected

Zika virus is best described as a(n) _________ virus with a ________ genome.

enveloped, ssRNA+

During lytic replication of bacteriophage, which process uses factors from the host cell, rather than coded by the viral genome?

enzymes which transcribe and translate viral genes

When a virus has an envelope,:

it likely escapes it host cell by budding.

Prions are:

misfolded proteins which can cause normal versions to also misfold.

The most common drugs that block replication are ________.

nuceloside analogs

What does the plaque assay determine?

number of bacteriophage in a sample

Viruses do not infect which of the following organisms? a) Animals b) Viruses can infect all forms of life. c) Fungi d) Bacteria

b) Viruses can infect all forms of life.

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?

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

Which type of method is used to determine if a prior exposure to a virus occurred?

Latex agglutination test

An individual uses an in-home test kit one week after engaging in high-risk behavior for HIV infection. The test kit uses a saliva sample that is mailed to a lab where an agglutination test to detected HIV antibodies is run. The results come back negative for HIV. What should the patient consider regarding these test results?

One week may not be enough time for HIV antibodies to be detected.

Why is there a need to be vaccinated with a new flu shot every year?

The RNA genome of influenza mutates frequently, causing minor changes. This is referred to as antigenic drift.

What is a key difference between lytic and lysogenic bacteriophage replication cycles?

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

One ml of a liquid suspension of bacteriophage is mixed with its host bacteria and plated. After incubation, the plate is completely clear. What is the probable explanation?

The phage concentration was so high that all the host bacterial cells were killed.

Which of the following statements incorrectly describes viral spikes? a) Lipid-based spikes make up the envelope that surrounds the capsid. b) Spikes are glycoprotein extensions that help viruses attach and gain entry to host cells. c) Spikes may be recognized by the host immune system that mounts an immune response to them. d) Spikes have an important role in determining what species and tissues the virus can infect.

a) Lipid-based spikes make up the envelope that surrounds the capsid.

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 releases from host cells by budding. b) Replication occurs in the nucleus of the host cell. c) The virus does not undergo uncoating. d) The virus undergoes lysogenic replication.

a) The virus releases from host cells by budding.

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

a) skin cancer

In a(n) _________ infection, viral replication peaks, followed by immune clearance of the virus.

acute

Viral spikes:

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.

Which of the following oncogenic viruses may integrate into the host genome? a) Epstein-Barr viruses b) Human papilloma viruses (HPVs) c) Hepatitis C viruses d) Human herpes virus-8

b) Human papilloma viruses (HPVs)

Which of the following are contributors to viral genome evolution? a) superior proofreading by RNA polymerases compared to DNA polymerases b) quick replication time and the large number of virions released within a host c) the large number of virions released within a host d) quick replication time and superior proofreading by RNA polymerases compared to DNA polymerases e) quick replication time

b) quick replication time and the large number of virions released within a host

Viruses which infect many different tissues types are said to have a(n):

broad tropism.

Which of the following is a major difference between bacteriophages and animal viruses? a) Animal viruses are assembled in the cytoplasm of cells; bacteriophages are assembled in the nucleus of a bacterial cell. b) Animal viruses are released from the cell by bursting; bacteriophages are released by budding. c) Animal viruses enter the host cell; bacteriophages inject their genome into the host without entering. d) There are no differences between animal viruses and bacteriophages.

c) Animal viruses enter the host cell; bacteriophages inject their genome into the host without entering.

Which of the following methods is used to cultivate bacteriophages in the laboratory setting? a) Bacteriophages are cultivated in tissue cultures. b) Bacteriophages are cultivated in embryonated eggs. c) Bacteriophages are cultivated in bacteria in liquid broth or on solid medium. d) Bacteriophages are grown with the streak plate method.

c) Bacteriophages are cultivated in bacteria in liquid broth or on solid medium.

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

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

Which of the following is not a mechanism of an antiviral drug? a) Blocking viral penetration b) Blocking uncoating c) Blocking viral ribosomes d) Blocking viral attachment

c) Blocking viral ribosomes

Which of the following is an unsuitable culture method for an animal virus? a) Tissue culture method b) Live animal inoculation c) Direct inoculation of virus onto blood agar d) Injection of virus into embryonated eggs

c) Direct inoculation of virus onto blood agar

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) Infected host cells will carry a provirus until sufficient viral load has been reached. 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) Viral replication occurs as a steady, logarithmic increase over time.

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

Which of the following terms is used to describe the shape of a virus? a) Coccus b) Spirillum c) Icosahedral d) Bacillus

c) Icosahedral

Which of the following steps is found in the lysogenic replication pathway but not in the lytic replication pathway? a) Penetration b) Attachment c) Integration d) Assembly

c) Integration

A nurse experienced an accidental needle stick while treating a patient who has hepatitis C. The seroconversion window for hepatitis C is approximately 6-8 weeks. Given this information, which of the following viral detection methods would be most appropriate for detecting a hepatitis C infection in the nurse one week following the needle stick? a) Modified latex agglutination test for detection of anti-hepatitis C antibodies b) Plaque assay c) PCR-based detection of hepatitis C RNA d) ELISA-based detection of anti-hepatitis C antibodies

c) PCR-based detection of hepatitis C RNA

Which of the following acellular agents do not have any genetic material and therefore do not replicate? a) Bacteria b) Protists c) Prions d) Archaea

c) Prions

Nucleic acid detection techniques:

can detect new viruses and early-stage infections that antibody-antigen tests are likely to miss.

Choose the correct statement about viral evolution. a) DNA viruses mutate faster than RNA viruses because thymine is more susceptible to mutation than uracil. b) RNA and DNA viral genomes evolve at equal rates. c) Cellular genomes mutate at a faster rate than viral genomes due to their large size and increased chance of replicative mistakes. d) RNA viruses mutate faster than DNA viruses due to a lack of proofreading replicative enzymes.

d) RNA viruses mutate faster than DNA viruses due to a lack of proofreading replicative enzymes.

Which of the following is not a property used to group viruses? a) Capsid symmetry (helical, icosahedral, or complex) b) Type of nucleic acid present (DNA or RNA) c) Presence or absence of an envelope d) Unicellularity versus multicellularity

d) Unicellularity versus multicellularity

Which of the following viral genomes is immediately ready for translation after the virus gains entry into the cell? a) ssDNA b) dsRNA c) dsDNA d) ssRNA+

d) ssRNA+

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

d) variant CJD

A previously undescribed infection has been detected among inhabitants in an isolated village in a remote tropical rainforest. When serum from an infected individual is passed through a filter, the infection can be transmitted to laboratory animals. Nothing is observed when the serum is examined with a light microscope at the highest magnification. Biochemical tests show the presence of RNA and protein but no carbohydrates or lipids. This data is consistent with what type of infectious agent?

virus

Challenges in developing effective antiviral drugs with minimal side effects to the patient include...

viruses use the cell's own machinery and metabolism for replication.