Basic Biology Practice Test: Viruses | Practice Test / Quiz / MCQs

1. Which of the following represents a difference between viruses and viroids?

Viruses cannot pass through plasmodesmata, whereas viroids can.Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.Viruses contain introns, whereas viroids have only exons.Viruses have capsids composed of protein, whereas viroids have no capsids.Viruses always have genomes composed of DNA , whereas viroids always have genomes composed of RNA

3. 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?

re-infection by the same herpesvirus strainre-infection by a closely related herpesvirus of a different strainco-infection with an unrelated virus that causes the same symptomscopies of the herpesvirus genome permanently maintained in host nucleicopies of the herpesvirus genome permanently maintained in host cell cytoplasm

4. What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for making complementary RNA strands.It hydrolyzes the host cell's DNA It translates viral RNA into proteins.It converts host cell RNA into viral DNA It uses viral RNA as a template for DNA synthesis.

5. Viral genomes vary greatly in size and may include from four genes to several hundred genes. Which of the following viral features is most apt to correlate with the size of the genome?

size and shape of the capsidglycoproteins of the envelopeRNA versus DNA genomedouble- versus single-strand genomessize of the viral capsomeres

6. RNA viruses require their own supply of certain enzymes because

these enzymes penetrate host cell membranes.host cells rapidly destroy the viruses.these enzymes cannot be made in host cells.host cells lack enzymes that can replicate the viral genome.these enzymes translate viral mRNA into proteins.

7. To cause a human pandemic, the H5N1 avian flu virus would have to

develop into a virus with a different host range.become much more pathogenic.spread to primates such as chimpanzees.arise independently in chickens in North and South America.become capable of human-to-human transmission.

8. Antiviral drugs that have become useful are usually associated with which of the following properties?

ability to remove all viruses from the infected hostremoval of viral proteinsprevention of the host from becoming infectedinterference with viral replicationremoval of viral mRNAs

9. The host range of a virus is determined by

the proteins in the host's cytoplasm.the proteins on its surface and that of the host.whether its nucleic acid is DNA or RNAthe enzymes produced by the virus before it infects the cell.the enzymes carried by the virus.

10. 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

T4 protein and T4 DNA T2 protein and T4 DNA a mixture of the DNA and proteins of both phages.T2 protein and T2 DNA T4 protein and T2 DNA

11. Which of the following describes plant virus infections?

They are spread via the plasmodesmata.They can never be passed vertically.They can be controlled by the use of antibiotics.They are seldom spread by insects.They have little effect on plant growth.

12. 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?

herpesvirusrabiesHIVsmallpoxhepatitis virus

13. 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?

control of more than one gene in an operonpositive control mechanisms rather than negativeutilization of eukaryotic polymerasesreliance on transcription activatorsregulation via acetylation of histones

14. Which of the following is characteristic of the lytic cycle?

Viral DNA is incorporated into the host genome.The virus-host relationship usually lasts for generations.The viral genome replicates without destroying the host.Many bacterial cells containing viral DNA are produced.A large number of phages are released at a time.

15. Which of the following statements describes the lysogenic cycle of lambda (λ) phage?

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

16. What are prions?

mobile segments of DNA viruses that invade bacteriamisfolded versions of normal brain proteintiny molecules of RNA that infect plantsviral DNA that has had to attach itself to the host genome

17. 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?

The plants would develop some but not all of the symptoms of the TMV infection.The plants would develop symptoms typically produced by viroids.The plants would not show any disease symptoms.The plants would become infected, but the sap from these plants would be unable to infect other plants.The plants would develop the typical symptoms of TMV infection.

18. Why do RNA viruses appear to have higher rates of mutation?

Replication of their genomes does not involve proofreading.RNA nucleotides are more unstable than DNA nucleotides.RNA viruses are more sensitive to mutagens.RNA viruses replicate faster.RNA viruses can incorporate a variety of nonstandard bases.

19. Which of the following is the best predictor of how much damage a virus causes?

ability of the infected cell to undergo normal cell divisionwhether the viral mRNA can be transcribedwhether the infected cell produces viral proteinability of the infected cell to carry on translationhow much toxin the virus produces

20. Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host?

The newly emerging virus will die out rather quickly or will mutate to be far less lethal.A change in environmental conditions such as weather patterns quickly forces the new virus to invade new areas.The new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts.It is able to spread to a large number of new hosts quickly because the new hosts have no immunological memory of them.Sporadic outbreaks will be followed almost immediately by a widespread pandemic.

21. The difference between vertical and horizontal transmission of plant viruses is that

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.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.vertical transmission is the spread of viruses from upper leaves to lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level.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.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.

22. Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory?

Viruses contain either DNA or RNAViruses can reproduce only inside host cells.Viruses are enclosed in protein capsids rather than plasma membranes.Viruses can infect both prokaryotic and eukaryotic cells.Viral genomes are usually similar to the genome of the host cell.

23. Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

ribosomescell divisionmetabolismindependent existencegenetic material composed of nucleic acid

24. Which of the following series best reflects what we know about how the flu virus moves between species?

An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans.A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.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, the virus mutates and can be transmitted to humans.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.

25. Viral envelopes can best be analyzed with which of the following techniques?

antibodies against specific proteins not found in the host membranesstaining and visualization with the light microscopetransmission electron microscopyimmunofluorescent tagging of capsid proteinsuse of plaque assays for quantitative measurement of viral titer

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25 Questions

❤ If you liked Fatskills, consider supporting us by checking out The Life Manuals You Never Got.

About | Explore | User Guide | Topics | Subjects | Doubt Solver | Career Aptitude Test | Answers | Free Tools | What Should We Know? Privacy | Terms |

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All trademarks, logos and brand names are the property of their respective owners. All company, product and service names used in this website are for identification purposes only. Use of these names, trademarks and brands does not imply endorsement.

About | Explore | User Guide | Topics | Subjects | Doubt Solver | Career Aptitude Test | Answers | Free Tools | What Should We Know?
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Without work one finishes nothing. - Ralph Waldo Emerson
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