Chapter 19 Test (1-10) Flashcards
Which of the following represents a difference between viruses and viroids?
A) Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.
B) Viruses contain introns, whereas viroids have only exons.
C) Viruses have capsids composed of protein, whereas viroids have no capsids.
D) Viruses always have genomes composed of DNA, whereas viroids always have genomes composed of RNA.
E) Viruses cannot pass through plasmodesmata, whereas viroids can.
C) Viruses have capsids composed of protein, whereas viroids have no capsids.
A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?
A) The plants would become infected, but the sap from these plants would be unable to infect other plants.
B) The plants would develop symptoms typically produced by viroids.
C) The plants would develop the typical symptoms of TMV infection.
D) The plants would develop some but not all of the symptoms of the TMV infection.
E) The plants would not show any disease symptoms.
C) The plants would develop the typical symptoms of TMV infection.
Which viruses have single-stranded RNA that acts as a template for DNA synthesis?
A) lytic phages
B) retroviruses
C) bacteriophages
D) proviruses
E) viroids
B) retroviruses
What is difference between an epidemic and a pandemic?
A) An epidemic is restricted to a local region; a pandemic is more global.
B) An epidemic is caused by a bacterial infection; a pandemic is caused by a viral infection.
C) An epidemic is a disease; a pandemic is a treatment.
D) An epidemic is a disease that spreads or becomes more common; a pandemic is a disease that remains stable in terms of numbers affected.
E) An epidemic is a disease with fairly low mortality; a pandemic has a much higher mortality rate.
A) An epidemic is restricted to a local region; a pandemic is more global.
RNA viruses require their own supply of certain enzymes because
A) these enzymes translate viral mRNA into proteins.
B) these enzymes cannot be made in host cells.
C) host cells lack enzymes that can replicate the viral genome.
D) host cells rapidly destroy the viruses.
E) these enzymes penetrate host cell membranes.
C) host cells lack enzymes that can replicate the viral genome.
Most human-infecting viruses are maintained in the human population only. However, a zoonosis is a disease that is transmitted from other vertebrates to humans, at least sporadically, without requiring viral mutation. Which of the following is the best example of a zoonosis?
A) HIV
B) rabies
C) herpesvirus
D) hepatitis virus
E) smallpox
B) rabies
The host range of a virus is determined by
A) the enzymes carried by the virus.
B) the proteins on its surface and that of the host.
C) the enzymes produced by the virus before it infects the cell.
D) the proteins in the host’s cytoplasm.
E) whether its nucleic acid is DNA or RNA.
B) the proteins on its surface and that of the host.
Which of the following characteristics, structures, or processes is common to both bacteria and viruses?
A) genetic material composed of nucleic acid
B) cell division
C) metabolism
D) independent existence
E) ribosomes
A) genetic material composed of nucleic acid
Which of the following statements describes the lysogenic cycle of lambda (λ) phage?
A) Most of the prophage genes are activated by the product of a particular prophage gene.
B) Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic.
C) After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
D) The phage genome replicates along with the host genome.
E) The phage DNA is incorporated by crossing over into any nonspecific site on the host cell’s DNA.
D) The phage genome replicates along with the host genome.
Which of the following accounts for someone who has had a herpesvirus-mediated cold sore or genital sore getting flare-ups for the rest of his or her life?
A) copies of the herpesvirus genome permanently maintained in host nuclei
B) re -infection by a closely related herpesvirus of a different strain
C) re -infection by the same herpesvirus strain
D) co-infection with an unrelated virus that causes the same symptoms
E) copies of the herpesvirus genome permanently maintained in host cell cytoplasm
A) copies of the herpesvirus genome permanently maintained in host nuclei
