++
++
++
++
Some viruses are characterized by helical symmetry of the viral nucleocapsid. Which of the following statements about viruses with helical symmetry is most accurate?
++
++
++
(A) All enveloped viruses with helical symmetry are classified into the same virus family.
++
++
(B) Helical nucleocapsids are found primarily in DNA-containing viruses.
++
++
(C) All human viruses with helical nucleocapsids possess an envelope.
++
++
(D) Excess empty helical particles containing no nucleic acid are commonly produced in infected cells.
++
++
++
Virus-infected cells often develop morphologic changes referred to as cytopathic effects. Which of the following statements about virus-induced cytopathic changes is most accurate?
++
++
++
(A) They are pathognomonic for an infecting virus.
++
++
(B) They are rarely associated with cell death.
++
++
(C) They may include giant cell formation.
++
++
(D) They can only be seen with an electron microscope.
++
++
++
Viruses usually initiate infection by first interacting with receptors on the surface of cells. Which of the following statements is most accurate about cellular receptors for viruses?
++
++
++
(A) Cellular receptors for viruses have no known cellular function.
++
++
(B) All viruses within a given family use the same cellular receptor.
++
++
(C) All cells in a susceptible host express the viral receptor.
++
++
(D) Successful infection of a cell by a virus may involve interaction with more than one type of receptor.
++
++
++
Which of the following can be used to quantitate the titer of infectious viruses?
++
++
++
++
++
++
++
++
++
(D) Polymerase chain reaction
++
++
++
++
++
Which one of the following states a principle regarding viral nucleic acid?
++
++
++
(A) Viruses contain both RNA and DNA.
++
++
(B) Some viruses contain a segmented genome.
++
++
(C) Purified viral nucleic acid from any virus is usually infectious.
++
++
(D) Viral genome sizes are similar among known human viruses.
++
++
++
Two mutants of poliovirus have been isolated, one (MutX) with a mutation in gene X and the second (MutY) with a mutation in gene Y. If cells are infected with each mutant alone, no virus is produced. If a cell is coinfected with both MutX and MutY, which one of the following is most likely to occur?
++
++
++
(A) Reassortment of genome segments may occur and give rise to a viable wild-type virus.
++
++
(B) The genomes may be reverse transcribed to DNA and both MutX and MutY viruses produced.
++
++
(C) Complementation between the mutant gene products may occur and both MutX and MutY viruses produced.
++
++
(D) The cells will transform at high frequency because they will not be killed by the poliovirus mutants.
++
++
++
Which one of the following viruses possesses an RNA genome that is infectious when purified?
++
++
++
++
++
++
++
++
++
++
++
++
++
++
Viruses belonging to which of the following groups are likely to establish latent infections?
++
++
++
++
++
++
++
++
++
++
++
++
++
++
Some viruses encode for a viral RNA-dependent RNA polymerase. Which of the following states a principle about viral RNA polymerases?
++
++
++
(A) All RNA viruses carry RNA polymerase molecules inside virus particles because they are needed to initiate the next infectious cycle.
++
++
(B) Antibodies against the viral RNA polymerase neutralize virus infectivity.
++
++
(C) Negative-strand RNA viruses supply their own RNA-dependent RNA polymerase because eukaryotic cells lack such enzymes.
++
++
(D) The viral RNA polymerase protein also serves as a major core structural protein in the virus particle.
++
++
++
Which of the following statements regarding virus morphology is true?
++
++
++
(A) All RNA viruses are spherical in shape.
++
++
(B) Some viruses contain flagella.
++
++
(C) Some viruses with DNA genomes contain a primitive nucleus.
++
++
(D) Viral surface proteins protect the viral genome from nucleases.
++
++
(E) Helical nucleocapsids are found with single-stranded DNA viruses.
++
++
++
Many viruses can be grown in the laboratory. Which of the following statements about virus propagation is not true?
++
++
++
(A) Some viruses can be propagated in cell-free media.
++
++
(B) Some mammalian viruses can be cultivated in hen’s eggs.
++
++
(C) Some viruses with broad host ranges can multiply in many types of cells.
++
++
(D) Some human viruses can be grown in mice.
++
++
(E) Most virus preparations have particle-to-infectious unit ratios greater than 1.
++
++
++
Laboratory infections can be acquired when working with viruses unless good laboratory safety practices are followed. Which of the following is not a good biosafety practice?
++
++
++
(A) Use of biosafety hoods
++
++
(B) Use of laboratory coats and gloves
++
++
(C) Avoidance of pipetting by mouth
++
++
(D) Flushing experimental waste down laboratory sink
++
++
(E) Not eating or drinking in the laboratory
++
++
++
Small viruses are in the same size range as which of the following?
++
++
++
(A) Staphylococcus species
++
++
++
++
++
++
++
++
++
++
++
Which of the following is not an important factor contributing to the phenomenon of emerging viral diseases?
++
++
++
(A) International air travel
++
++
(B) Antibiotic resistance
++
++
++
++
++
++
(E) Organ and tissue transplantation
++
++
++
Arboviruses are classified into several different virus families but are grouped together based on which of the following common characteristics?
++
++
++
(A) Replicate only in humans
++
++
(B) Contain both RNA and DNA
++
++
(C) Are transmitted by vectors
++
++
(D) Cause hemorrhagic fevers
++
++