Bio Ch. 17

Which of the following describes plant virus infections? A) They can be controlled by the use of antibiotics. B) They are spread via the plasmodesmata. C) They have little effect on plant growth. D) They are seldom spread by insects. E) They can never be passed vertically.

B

Which of the following is the best predictor of how much damage a virus causes? A) ability of the infected cell to undergo normal cell division B) ability of the infected cell to carry on translation C) whether the infected cell produces viral protein D) whether the viral mRNA can be transcribed E) how much toxin the virus produces

A

Antiviral drugs that have become useful are usually associated with which of the following properties? A) ability to remove all viruses from the infected host B) interference with viral replication C) prevention of the host from becoming infected D) removal of viral proteins E) removal of viral mRNAs

B

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced will 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

Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory? A) Viruses contain either DNA or RNA. B) Viruses are enclosed in protein capsids rather than plasma membranes. C) Viruses can reproduce only inside host cells. D) Viruses can infect both prokaryotic and eukaryotic cells. E) Viral genomes are usually similar to the genome of the host cell.

E

Which viruses have single-stranded RNA that acts as a template for DNA synthesis? A) lytic phages B) proviruses C) viroids D) bacteriophages E) retroviruses

E

The difference between vertical and horizontal transmission of plant viruses is that A) vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant. B) vertical transmission is the spread of viruses from the upper leaves to the lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level. C) vertical transmission is the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size. D) vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type. E) vertical transmission is the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species.

A

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

Viral envelopes can best be analyzed with which of the following techniques? A) use of 15N to label specific nucleotides B) antibodies against specific proteins not found in the host membranes C) DNA staining and visualization with the light microscope D) use of plaque assays for quantitative measurement of viral titer E) immunofluorescent tagging of capsid proteins

B

What is the function of reverse transcriptase in retroviruses? A) It hydrolyzes the host cell's 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

Which of the following can be effective in preventing the onset of viral infection in humans? A) taking vitamins B) getting vaccinated C) taking antibiotics D) applying antiseptics E) taking nucleoside analogs that inhibit transcription

B

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 proofreading. C) RNA viruses replicate faster. D) RNA viruses can incorporate a variety of nonstandard bases. E) RNA viruses are more sensitive to mutagens.

B

A human pandemic is A) a viral disease that infects all humans. B) a flu that kills more than 1 million people. C) an epidemic that extends around the world. D) a viral disease that can infect multiple species. E) a virus that increases in mortality rate as it spreads.

C

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

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following would you expect of the genes of the bacteriophage? A) regulation via acetylation of histones B) positive control mechanisms rather than negative C) control of more than one gene in an operon D) reliance on transcription activators E) utilization of eukaryotic polymerases

C

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

Which of the following statements describes the lysogenic cycle of lambda (λ) phage? A) After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses. B) Most of the prophage genes are activated by the product of a particular prophage gene. C) The phage genome replicates along with the host genome. D) Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic. E) The phage DNA is incorporated by crossing over into any nonspecific site on the host cell's DNA.

C

Emerging viruses arise by A) mutation of existing viruses. B) the spread of existing viruses to new host species. C) the spread of existing viruses more widely within their host species. D) all of the above E) none of the above

D

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) re-infection by a closely related herpesvirus of a different strain B) re-infection by the same herpesvirus strain C) co-infection with an unrelated virus that causes the same symptoms D) copies of the herpesvirus genome permanently maintained in host nuclei E) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

D

Which of the following is characteristic of the lytic cycle? 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 are released at a time. E) The virus-host relationship usually lasts for generations.

D

The host range of a virus is determined by A) the enzymes carried by the virus. B) whether its nucleic acid is DNA or RNA. C) the proteins in the host's cytoplasm. D) the enzymes produced by the virus before it infects the cell. E) the proteins on its surface and that of the host.

E

Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host? A) It is able to spread to a large number of new hosts quickly because the new hosts have no immunological memory of them. B) The new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts. C) A change in environmental conditions such as weather patterns quickly forces the new virus to invade new areas. D) Sporadic outbreaks will be followed almost immediately by a widespread pandemic. E) The newly emerging virus will die out rather quickly or will mutate to be far less lethal.

E

Which of the following series best reflects what we know about how the flu virus moves between species? A) An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans. B) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. C) A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans. D) An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host. E) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, and the virus mutates and can be transmitted to humans.

E