Chapter 19 Preparatory Questions

1) Why are viruses referred to as obligate parasites? A) They cannot reproduce outside of a host cell. B) Viral DNA always inserts itself into host DNA. C) They invariably kill any cell they infect. D) They can incorporate nucleic acids from other viruses. E) They must use enzymes encoded by the virus itself.

A) They cannot reproduce outside of a host cell

2) Which of the following molecules make up the viral envelope? A) glycoproteins B) proteosugars C) carbopeptides D) peptidocarbs E) carboproteins

A) glycoproteins

7) What is the name given to viruses that are single-stranded RNA that acts as a template for DNA synthesis? A) retroviruses B) proviruses C) viroids D) bacteriophages E) lytic phages

A) retroviruses

8) What is the function of reverse transcriptase in retroviruses? A) It hydrolyzes the host cellʹs DNA. B) It uses viral RNA as a template for DNA synthesis. C) It converts host cell RNA into viral DNA. D) It translates viral RNA into proteins. E) It uses viral RNA as a template for making complementary RNA strands

B) It uses viral RNA as a template for DNA synthesis.

5) Why do RNA viruses appear to have higher rates of mutation? A) RNA nucleotides are more unstable than DNA nucleotides. B) Replication of their genomes does not involve the proofreading steps of DNA replication. C) RNA viruses replicate faster. D) RNA viruses can incorporate a variety of nonstandard bases. E) RNA viruses are more sensitive to mutagens.

B) Replication of their genomes does not involve the proofreading steps of DNA replication *DNA polymerase

4) Which of the following is characteristic of the lytic cycle accompanying infection by bacteriophage? A) Many bacterial cells containing viral DNA are produced. B) Viral DNA is incorporated into the host genome. C) The viral genome replicates without destroying the host. D) A large number of phages is released at a time. E) The virus-host relationship usually lasts for generations.

B) Viral DNA is incorporated into the host genome.

10) RNA viruses require their own supply of certain enzymes because A) host cells rapidly destroy the viruses. B) host cells lack enzymes that can replicate the viral genome. C) these enzymes translate viral mRNA into proteins. D) these enzymes penetrate host cell membranes. E) these enzymes cannot be made in host cells.

B) host cells lack enzymes that can replicate the viral genome.

6) 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 develop some but not all of the symptoms of the TMV infection. 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 not show any disease symptoms. E) The plants would become infected, but the sap from these plants would be unable to infect other plants.

C) The plants would develop the typical symptoms of TMV infection *Infected cell to non-infected cells

12) To cause a human pandemic, the H5N1 avian flu virus would have to A) spread to primates such as chimpanzees. B) develop into a virus with a different host range. C) become capable of human-to-human transmission. D) arise independently in chickens in North and South America. E) become much more pathogenic.

C) become capable of human-to-human transmission.

11) Which of the following characteristics, structures, or processes is common to both bacteria and viruses? A) metabolism B) ribosomes C) genetic material composed of nucleic acid D) cell division E) independent existence

C) genetic material composed of nucleic acid

9) A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have A) T2 protein and T4 DNA. B) T2 protein and T2 DNA. C) a mixture of the DNA and proteins of both phages. D) T4 protein and T4 DNA. E) T4 protein and T2 DNA

D) T4 protein and T4 DNA.

3) Which of the following accounts for someone who has had a virus-mediated sore getting flare-ups for the rest of life? A) re-infection by a closely related virus of a different strain B) re-infection by the same viral strain C) co-infection with an unrelated virus that causes the same symptoms D) copies of the viral genome permanently maintained in host nuclei E) copies of the viral genome permanently maintained in host cell cytoplasm

D) copies of the viral genome permanently maintained in host nuclei