BIO 226 CHAPTER 13 EXAM QUESTIONS AND ANSWERS

• List ways in which bacteria and viruses are different? Are there ways that they are similar? Similarities Differences Both can cause disease Bacteria are unicellular living organism WHILE virus are non-living and have no cells Both do not have a nuclei Bacteria are larger in size(1000nm) while viruses are small (20-400nm) Both can be spread by contact with contaminated people or items Bacteria reproduces by binary fission while viruses reproduce by invading a host cell and copying the DNA/RNA Both are capable of killing humans and raging human health. Bacteria is localized while virus is systematic Bacteria is usually treated with antibiotics while viruses will not be affected by antibiotics • Describe the chemical and physical structure of both enveloped and nonenveloped viruses. o What are the essential features of all viruses? Essential features in all viruses are DNA or RNA and a protein coat (capsid) o What features are found in some, but not all viruses? Features such as an envelope (phospholipid bilayer) and spikes are found in some viruses. • How do enveloped viruses acquire their envelope? An enveloped virus obtains its envelope by being released from the host cell, and taking a bit of its cell membrane. • Which is easier to disinfect enveloped or noneveloped viruses? Enveloped viruses • What are spikes? How are they used to help viruses cause infections? Hemaglutinin (H) spikes are used for attachment to host cells. The Neuramindase (N) spikes help to release virus from cells. • Why are viruses said to be host and cell specific? Viruses are host and cell specific because they only infect specific types of cells in one host • Describe the difference between antigenic shift and antigenic drift? Antigenic drifts are minor changes to a H or N spikes, might involve only one amino acid, just enough to allow virus to avoid mucosal antibodies WHILE Antigenic shifts are major changes in H or N spikes and are probably due to genetic recombination between different strains infecting the same cell. o How does this account for changes in influenzae from season to season? The small changes that occur from antigenic drift usually produce viruses that are closely related to one another. When antigenic drift occurs, the body’s immune system may not recognize and prevent sickness caused by the newer influenza viruses. As a result, a person becomes susceptible to flu infection again, Shift can result in a new influenza A subtype in humans. One way shift can happen is when an influenza virus from an animal population gains the ability to infect humans. Such animal-origin viruses can contain an HA or HA/NA combination that is so different from the same subtype in humans that most people do not have immunity to the new (e.g., novel) virus. • What are the conditions necessary for a Flu pandemic? o New influenza subtype with little or no human immunity o Must infect humans and cause illness o Must spread easily among humans • Describe how bacteriophages are cultured. We take a lawn of bacteria and infect it with bacteriophages. We know it’s been infected when a clearing (plaque) is formed on the surface. • Describe how animal viruses are cultured. They are grown in living animals or in embryonated eggs. Now they may be grown in cell culture. o What are the different types of cell lines used? Continuous cell lines, Primary cell lines and Diploid cell lines. • Describe the lytic and lysogenic cycles of bacteriophages. In the lytic cycle, the virus attaches by the tail fibers to host cell and use lysozymes to poke a hole in cell wall and puts a sheath through to force DNA into cell. The DNA hijacks the host to produce phage DNA and proteins. The phage particles are then assembled and the virus uses lysozyme to break out of cell. In the lysogenic cycle, the phage DNA incorporates into the host genome as what is known as a prophage. It is replicated when the bacterial cell itself is undergoing division