biology chapter 19

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.

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 three types of viruses shown above would you expect to include a capsid(s)?

all three

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

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

antibodies against specific proteins not found in the host membranes

RNA viruses require their own supply of certain enzymes because

host cells lack enzymes that can replicate the viral genome.

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

genetic material composed of nucleic acid

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

getting vaccinated

In the figure, at the arrow marked II, what enzyme(s) are being utilized?

host cell DNA polymerase

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

Which viruses have single-stranded RNA that acts as a template for DNA synthesis?

retroviruses

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

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 is characteristic of the lytic cycle?

A large number of phages is released at a time.

Of the possible arrangements of the sites given below, which one is most likely?

B

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

Replication of their genomes does not involve proofreading.

Which treatment could definitively determine whether or not the component is a viroid?

I

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

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

The phage genome replicates along with the host genome.

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

become capable of human-to-human transmission.

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

interference with viral replication

What is the function of reverse transcriptase in retroviruses?

it uses viral RNA as a template for DNA synthesis

What are prions?

misfiled versions of normal brain protein

Emerging viruses arise by

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.

In the figure, when new viruses are being assembled (IV), what mediates the assembly?

nothing; they self-assemble