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

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

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

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

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

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

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.The newly emerging virus will die out rather quickly or will mutate to be far less lethal.Sporadic outbreaks will be followed almost immediately by a widespread pandemic.

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

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

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

The phage genome replicates along with the host genome.The phage DNA is incorporated by crossing over into any nonspecific site on the host cell's DNA 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.After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.

6. 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.become capable of human-to-human transmission.arise independently in chickens in North and South America.spread to primates such as chimpanzees.

7. Emerging viruses arise by

the spread of existing viruses more widely within their host species.none of these.mutation of existing viruses.mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species.the spread of existing viruses to new host species.

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

immunofluorescent tagging of capsid proteinsstaining and visualization with the light microscopeuse of plaque assays for quantitative measurement of viral titerantibodies against specific proteins not found in the host membranestransmission electron microscopy

9. 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?

regulation via acetylation of histonesutilization of eukaryotic polymerasespositive control mechanisms rather than negativereliance on transcription activatorscontrol of more than one gene in an operon

10. 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?

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

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

removal of viral mRNAsability to remove all viruses from the infected hostremoval of viral proteinsprevention of the host from becoming infectedinterference with viral replication

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?

hepatitis virussmallpoxrabiesherpesvirusHIV

14. 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?

double- versus single-strand genomessize of the viral capsomeresRNA versus DNA genomesize and shape of the capsidglycoproteins of the envelope

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

independent existencemetabolismribosomescell divisiongenetic material composed of nucleic acid

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

host cells rapidly destroy the viruses.these enzymes penetrate host cell membranes.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.

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

how much toxin the virus producesability of the infected cell to carry on translationwhether the viral mRNA can be transcribedwhether the infected cell produces viral proteinability of the infected cell to undergo normal cell division

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

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 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.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 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.

19. Which of the following describes plant virus infections?

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

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

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

21. The host range of a virus is determined by

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

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

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

23. What are prions?

mobile segments of DNA viruses that invade bacteriaviral DNA that has had to attach itself to the host genometiny molecules of RNA that infect plantsmisfolded versions of normal brain protein

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.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.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.A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.

25. Which of the following can be effective in preventing the onset of viral infection in humans?

getting vaccinatedapplying antisepticstaking nucleoside analogs that inhibit transcriptiontaking antibioticstaking vitamins

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25 Questions

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

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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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