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