Chapter 36 Viruses Practice Test

Which of the following statements about emerging viruses is true?

Emerging viruses can arise by switching host species or by genome arrangement.

How do enveloped viruses differ from nonenveloped viruses?

Enveloped viruses have a membrane-like outer covering whereas nonenveloped viruses do not.

Which of the following best describes why there is currently no vaccine for HIV?

HIV evolves very rapidly.

How does HIV kill its host?

HIV kills the host indirectly.

To identify the cell surface protein that HIV uses to enter T cells, researchers used antibodies to block different membrane proteins prior to HIV infection. What was inferred from the experiment?

HIV uses CD4 protein to gain entry to these cells.

Which of the following is true of the entry of HIV's capsid into a cell?

HIV's capsid entry requires a receptor, co-receptor, and membrane fusion.

Which of the following is one of the two urgent tasks that public health officials first undertake to prevent an outbreak from becoming an epidemic?

Identify the causative agent

Which of the following statements concerning virus entry into cells is true?

Viruses must somehow bypass both the cell membrane and cell wall (if present) to enter a cell and replicate.

Which of the following statements about viruses is true?

Viruses use cells to produce new generations of viruses.

Which viral genome type requires the fewest number of conceptual steps between arrival into a cell and translation?

+)ssRNA

Which of the following molecules provided by the host cell is required for replication of all viruses?

ATP

Which lineage of viruses is the largest?

Positive-sense, single-stranded RNA viruses

Considering that there are many RNA viruses and that RNA can be a catalytic molecule, how does this relate to one of the theories for the origins of viruses?

RNA genomes of some viruses descended from genes found in early inhabitants of the RNA world.

Why did researchers set out to find molecules that would obstruct reverse transcriptase before investigating other viral proteins?

Reverse transcriptase is not a normal part of a human cell's biosynthetic machinery.

Which of the following statements about the replication of a viral genome is true?

The genome is integrated into the host chromosome during lysogenic growth.

Which statement best describes people infected with HIV?

There may be a lag of 8-12 years between the initial infection and the onset of illness but virtually all people who become infected with the virus will die of AIDS.

Which of the following statements best describes the action of vaccines?

Vaccines contain antigens that stimulate immune system cells and "prime" the immune system for a subsequent infection with a particular virus.

Which of the following statements concerning the production of envelope proteins is true?

Viral mRNAs are translated by ribosomes attached to the rough ER.

What is the single feature that distinguishes a simple virus from plasmids?

Viruses have a protein coat or membrane-like envelope.

Natural selection favors alleles that allow viruses to _____.

replicate within a host