Exam 19: Viruses

Which of the following viruses would most likely have reverse transcriptase inside them?

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

Which of the following characteristics is typical of the lytic cycle of a bacteriophage?

Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5′ end, the RNA genome has a viral protein (VPg) instead of a 5′ cap. This is followed by a non-translated leader sequence, and then a single long protein-coding region (~7,000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acids similar in structure to those that are found in viruses and other organisms. Short-period use of the radioactive amino acids result in labelling of only very long proteins, while longer periods of labelling result in several different short polypeptides. What conclusion is most consistent with the results of the radioactive labelling experiment?

What are prions?

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins in the Golgi apparatus, which of the following processes could likely result?

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

Effective antiviral drugs are usually associated with which of the following properties?

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

- Which of the three types of viruses shown would you expect to include glycoproteins?

Which of the following events or characteristics accounts for someone who has had regular herpesvirus-mediated cold sores or genital sore flare-ups?

Which of the following characteristics correctly describes retroviruses?

The first class of antiviral drugs developed to treat HIV infection, such as AZT, were known as reverse "transcriptase inhibitors". How did these drugs carry out their functions?

Evidence suggests that factors that contribute towards the virulence of E. coli strain O157:H7, a bacterial strain reported to cause several food poisoning deaths, are caused by genes from a virus that infects bacteria. Considering this evidence, which of the following statements most likely explains how the O157:H7 population acquired the genetic variation that distinguishes the strain from harmless E. coli strains, such as those that reside in our intestines?

Which of the following statements is correct regarding viral infections in plants?

Emerging viruses arise by

Viruses use the host cell's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

The herpes viruses are important enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others. If scientists are trying to use what they know about the herpes simplex virus to devise a means of protecting other people from being infected, which of the following treatments would have the best chance of lowering the number of new cases of infection?

You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus or prion. You have four methods at your disposal to analyse the substance and determine the nature of the infectious agent. I. Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious. II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III. Culture the substance on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then determine whether the substance is still infectious. -If you already know that the infectious agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities?

Will treating a viral infection with antibiotics affect the course of the infection?