Biology 1201- Newcomer: Chapter 19 (beginning only)

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

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

Replication of their genomes does not involve the proofreading steps of DNA replication.

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 the typical symptoms of TMV infection.

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

Viruses have capsids composed of protein, whereas viroids have no capsids.

Which of the following describes plant virus infections?

They are spread throughout a plant by passing through the plasmodesmata.

Why are viruses referred to as obligate parasites?

They cannot reproduce outside of a host cell.

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 operon

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

antibodies against specific proteins not found in the host membranes

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

getting vaccinated

Which of the following molecules make up the viral envelope?

glycoproteins

Which of the following terms describes bacteriophage DNA that has become integrated into the host cell chromosome?

prophages

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?

rabies

What characteristics of electron microscopes make them most useful for studying viruses?

shorter wavelengths providing higher resolution

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 capsid

The host range of a virus is determined by

the proteins on its surface and that of the host.

Which of the following is characteristic of the lytic cycle?

A large number of phages is released at a time.

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

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.

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturingthesubstancebyitselfonnutritivemedium,awayfromanyplantcells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious Which treatment could definitively determine whether or not the component is a viroid?

I

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturingthesubstancebyitselfonnutritivemedium,awayfromanyplantcells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious If you already knew that the infectious agent was either bacterial or viral, which treatment would allow you to distinguish between these two possibilities?

III

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturingthesubstancebyitselfonnutritivemedium,awayfromanyplantcells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious Which treatment would you use to determine if the agent is a prion?

IV only

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.

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

The phage genome replicates along with the host genome.

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

Viral genomes are usually more similar to the genome of the host cell than to the genomes of viruses that infect other cell types.

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

ability of the infected cell to undergo normal cell division

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 life?

copies of the herpesvirus genome permanently maintained in host nuclei

What are prions?

misfolded versions of normal brain protein

What is the name given to viruses that are single-stranded RNA that acts as a template for DNA synthesis?

retroviruses

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

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.