Читать книгу Basic Virology - Martinez J. Hewlett - Страница 39

1 A good general rule concerning the replication of RNA viruses is that they require what kind of molecular process?

2 What is the role of a vector in the transmission of a viral infection?

3 It is said that viruses appear to “violate the cell theory” (“cells only arise from preexisting cells”). To which phase of a virus life cycle (growth curve) does this refer? What is the explanation for this phase of the growth curve?

4 Viruses are called “obligate intracellular parasites.” For which step of gene expression do all viruses completely depend on their host cell?

5 Viruses are said to “violate the cell theory,” indicating that there are differences between viruses and cells. The following table lists several features of either viruses or cells or both. Indicate which of these features is true for viruses and which for cells. In each case, write a “Yes” if the feature is true or a “No” if the feature is not true.FeatureCellsVirusesThe genetic information may be RNA rather than DNA.New individuals arise by binary fission of the parent.Proteins are translated from messenger RNAs.New individuals assemble by spontaneous association of subunit structures.

6 At this writing, the avian influenza H5N1 is transmitted from bird to bird, although it may, at some point, mutate to allow transmission from human to human. What feature of virus–host interaction does this characterize?