Exam 19: Viruses

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

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

Use the following information to answer the questions below. Some viruses can be crystallized and their structures analyzed. One such virus is Desmodium, or yellow mottle virus, which infects beans. This is a member of the tymovirus group and has a single-stranded RNA genome of ~6300 nucleotides. Its virion is 25-30 nm in diameter, and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere, which has icosahedral symmetry with 20 facets. -If this virus has capsomeres with 20 facets, how many proteins form each one?

Emerging viruses arise by

Viral disease in plants is spread through the population by

What are examples of mobile genetic elements?

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?

Use the following information to answer the next few questions. Poliovirus is a positive-sense RNA virus of the picornavirus group. At its 5' end, the RNA genome has a viral protein (VPg) instead of a 5' cap. This is followed by a nontranslated leader sequence, and then a single long protein coding region (~7000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. 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 part of the poliovirus would first interact with host cell ribosomes to mediate translation?

Which of the following describes plant virus infections?

Use the figure that follows to answer the questions below. -Which of the three types of viruses shown above would you expect to include a capsid(s)?

RNA viruses require their own supply of certain enzymes because

Use the following information to answer the questions below. Throughout history, human populations have been impacted by viral outbreaks. In the past 100 years we have seen several devastating epidemics and pandemics that have put people at risk. Worldwide, annual seasonal flu epidemics result in about three to five million cases of severe illness, and about 250 000 to 500 000 deaths annually. Most deaths associated with seasonal influenza in industrialized countries occur among people age 65 or older. In 2009, a new strain of influenza, H1N1, entered the global scene. Within the year it had spread to 207 countries, infected 600 000 people, and killed 8000 worldwide. The pandemic alert was raised and a coordinated, concerted effort around the world was implemented to bring this flu under control. H1N1 is most likely a variation of the Spanish flu (also called H1N1); this flu was responsible for over 40 million deaths worldwide in the pandemic of 1918 (killing over 2.5% of the entire human population in one year). -Considering the statistic of seasonal flu, why did this strain create such alarm?

The host range of a virus is determined by

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

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

Use the figure that follows to answer the questions below. -Which of the three types of viruses shown above would you expect to include glycoproteins?

Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host?

Use the following information to answer the following questions. In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. The table below shows the results of testing five viruses for nuclease specificity, the ability of the virus to act as an mRNA, and presence (+) or absence (-) of its own viral polymerase. -Given Baltimore's scheme, a positive sense single-stranded RNA virus such as the polio virus would be most closely related to which of the following?

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

Use the following information to answer the few questions. The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex (HSV) I and II, causing facial and genital lesions, and the varicella-zoster (VSV), causing chicken pox and shingles. Each of these three actively infect 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 then reactivate, replicate again, and be infectious to others. -If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection?