HW #8 (exam 3)

Which of the following is NOT a way in which viruses are different from living organisms?

Viruses are obligate parasites and no living organisms are obligate parasites.

Based on your knowledge of cellular and viral processes, which of the following would be (an) appropriate target(s) for antiviral drugs?

integrases

When describing the viral genome, which terms could be used?

ds RNA ss DNA ds DNA *All of the listed responses are correct.

Why does the structure of plant and bacterial cells illustrate the reason for having few enveloped viruses that infect these cells?

Plant and bacterial cells contain cell walls that limit the virus from budding out and obtaining the envelope

When determining the number of bacterial virus particles in a suspension, why is the number obtained always less than the actual viral titer?

Because all of the virus particles do not infect with 100% efficiency.

Lysogeny is unique to bacteriophages; similar relationships have not been found among the animal viruses.

False

Penetration requires that the entire virus is inserted within the host.

False

Viruses infecting ________ are typically the easiest to grow in the laboratory.

prokaryotes

A lytic infection results in death of the host cell.

True

ALL viral particles

are metabolically inert.

When solutions of host cells and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.

plaques

Some viruses, especially animal viruses, have an envelope surrounding their nucleocapsid. This envelope may have viral proteins embedded in it. Why are the viral proteins more readily recognized and targeted by the immune system than the envelope?

Enveloped viruses are often coated with animal cell membrane as they leave the cell. This membrane is a major component of the viral envelope. The viral proteins are more readily recognized by the immune system, as they are more distinct from the materials normally found in and on the cells. However, the envelope can contain several types of viral components as well.

Which statement is TRUE?

Many viruses contain their own nucleic acid polymerases.

Plaque assays are often used to estimate the number of virions in a sample of a particular volume (the titer). The count is given as plaque-forming units. Which of the following is NOT generally a concern that must be considered in evaluating the results of plaque assays?

The largest problem is that single viruses may create multiple plaques, resulting in overestimates of the number of viruses present.

Which of the following is true about viral infection?

Viruses are very specific in which cells they infect. For a virus to be taken up by a cell, it must find a cell with appropriate receptors on the surface. It cannot be taken up by cells without the appropriate receptors.

What are the minimal components needed for a virion?

capsid and genome

Viruses go through phases during which they are actively replicating and destructive to the host cell, or dormant within the host cell. During which part of the bacteriophage life cycle will the viral genome be replicated in synchrony with the host cell?

lysogenic phase

Which of the following groups contains some representatives with genomes that are so small that they may have as few as two genes?

RNA viruses

What is the benefit, for a virus, to be a temperate or lysogenic virus?

A single infection event can produce millions of new viral particles instead of hundreds of viral particles.

The term "phage" is generally reserved for the viruses that infect

Bacteria

Viruses rely on the host cell machinery to make new viruses, but they sometimes provide their own enzymes (such as reverse transcriptase, which is an RNA-dependent DNA polymerase). Which of the following types of enzymes would a virus need to provide in order to replicate within a cell? In other words, which of these enzymes would not normally be found in a cell unless a virus provided it?

RNA replicases (RNA-dependent RNA polymerases) for RNA viruses

Reverse transcriptase is a(n)

RNA-dependent DNA polymerase.

Some viruses have plus sense RNA genomes. Which of the following could describe one of those viruses?

a virus that contains RNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products

Viral replication is

independent of the host cell's DNA but dependent on the host cell's enzymes and metabolism.