Chapter 6 and 11: Viruses

Multiple Choice Identify the choice that best completes the statement or answers the question.

____ 1. The destruction of cells as a result of viral lysis can be observed as a: a. tissue culture d. plaque b. lawn e. host c. soft agar

____ 3. An icosahedral capsid has how many sides? a. 4 d. 10 b. 6 e. 20 c. 8

____ 4. In bacteriophage T4, the DNA genome is contained in the head, and binding to the host is facilitated by attachment of the: a. capsid d. envelope b. neck e. tegument c. tail fibers

____ 6. The genome of ______ssRNA viruses can serve directly as mRNA. a. positive-sense (+) d. double-stranded b. negative-sense (–) e. prion c. all

____ 8. What happens to the virus protein coat when a bacterial cell is infected? a. It enters the host cell with the viral genome. b. It remains on the outside of the host cell. c. It enters the host cell separately from the viral genome. d. It is released to attach to and inject another host cell. e. It becomes part of the host cell membrane.

____ 11. A key factor in the evolution of killer strains of influenza is that they: a. only have eight genes d. have a segmented genome b. have an RNA genome e. have a circular chromosome c. contain reverse transcriptase

____ 16. The influenza reassortment process is enhanced by a particular feature of the virus, namely the ______genome. a. linear d. single-stranded b. circular e. segmented c. double-stranded

____ 18. Which antiviral agent is currently used to treat influenza infections targeting viral neuraminidase? a. Tamiflu d. Acyclovir b. Pleconaril e. Vitravene c. Zidovudine

____ 19. The ______virus envelope proteins recognize the specific protein sequence of CD4 and CCR5 in order to attach and enter the host cell. a. HIV d. M13 b. influenza e. polio c. T4

____ 20. The causative agent of chickenpox is: a. herpes simplex virus 1 d. Epstein-Barr virus b. herpes simplex virus 2 e. HIV c. varicella-zoster virus

____ 21. Which of the following best describes the genome of the influenza virus? a. negative-strand segmented RNA d. positive-strand single-piece RNA b. positive-strand segmented RNA e. double-stranded RNA c. negative-strand single-piece RNA

____ 23. Some people are resistant to HIV infection because they: a. lack CD4 receptors on their macrophages b. lack CCR5 receptors on their macrophages c. lack macrophages d. produce proteases that destroy HIV e. all of the above

Short Answer

1. What are prions and how do they cause disease?

2. What is the viral envelope composed of? How does it differ from the bacterial cell envelope?

4. Some viruses require an RNA-dependent RNA polymerase. What does that mean? Using the same vernacular, what would you call the host cell RNA polymerase (RNA pol)? What would you call reverse transcriptase (RTase)?

5. Why do many RNA viruses encode their own RNA-dependent RNA polymerase and package them in viral particles? 12. The nucleocapsid of an enveloped virus was found to have 20 capsomers per face. How many capsomers total are there in each particle?

A. 200 B. About 2000 C. 400 D. About 4000 E. One can’t say, because the envelope size varies substantially for particles of any particular enveloped virus. ------

13. Which of the following protein types are always found on the surface of virus particles?

A. Ribosomal proteins B. Host antibodies C. Polymerases D. Proteins that bind to host receptors E. Two of the above ------

14. In class we discussed virus from the Herpes family. What do viruses in that family have in common?

A. Infection with any family member always results in serious symptoms B. They all have dsDNA genomes C. They all reside as latent particles in the host and can cause disease symptoms long after the initial infection D. Two of the above are correct E. Three of the above are correct ------

15. Which of the diseases listed below is not a result of infection by a member of the Herpes family?

A. Cold sores B. Shingles C. Chicken pox D. Roseola (also known as sixth disease) E. All of the above are caused by Herpes viruses ------

16. In class we discussed viral hepatitis. Which statement about viral hepatitis is not true.

A. It is always caused by enveloped viruses with ssDNA genomes B. It is an infection of the liver C. It is can passed by blood or intimate contact D. It can be deadly E. It can be mild ------

17. HIV is a retrovirus, and many of the earliest anti-HIV drugs targeted reverse transcriptase. What does reverse transcriptase do? A. Make DNA, using RNA as template B. Make ssRNA(+) using ssRNA(-) as a template C. Make ssRNA(-) using ssRNA(+) as a template D. Make RNA, using DNA as template E. All of the above ------

18. Which of the following molecules act as a host-cell receptor for HIV?

A. CD4 B. CCR5 C. AIDS docking complex D. CD4 and CCR5 E. AIDS docking complex and CCR5

24. Which of the following is considered an important host of influenza A virus?

A. Beavers, and other large, architecturally-overachieving, aquatic mammals B. Bonobo chimpanzees, and other primates that are organized into matriarchal social groups C. Ducks and other birds that spend quality leisure time at water/land interfaces D. Rats and other rodents that are commonly, but mistakenly, disparaged as dirty, garbage-eating, parasites E. Trout, and other cold-water game fish that live enjoyable lives in fresh, highly oxygenated water

28. Which of the following statements about Hepatitis B virus and HIV are true?

A. Both have genomes consisting of DNA. B. Both are transmitted by the similar types of "lifestyle practices" C. Neither is problematic in developed countries D. Effective vaccinations are currently available for both. E. None of the statements are true

7. New influenza pandemics are often associated with “antigenic shifts”. For example, the 1933 H2N2 virus was replaced in 1968 by an H3N2 influenza strain. Why is it that influenza is particularly likely to undergo such antigenic shifts? Check the most important reason from the list below: A) It has a segmented genome. B) It has an RNA genome. C) RNA dependent RNA-polymerizes are especially error prone. D) The HA molecule may not be cleaved properly during infection.

8. Which of the following statements about viruses is false? (Choose E if all are correct).

A. Viruses are unable to replicate on their own B. Viruses can sometimes be treated with penicillin C. Viruses can cause some types of cancer D. Viruses do not always kill their host cells E. All of the above are true

9. Influenza type H5N1 (avian flu) is a growing concern. The virus can infect humans, but not easily. What are the main worries about this virus?

A. That it will gain mutations that allow it to easily infect and replicate in humans. B. That it will undergo genetic shift. C. That it will be accidentally released from laboratory settings D. Two of the above E. A, B, and C are all correct.

11. What is meant by “antigenic drift” in influenza biology? Pick one. A) The slow spread of viral infection in crowded environments. B) Changes in viral proteins and their genes by mutation. C) The production of new hybrid viral particles following the infection of a single cell by two viral types D) The spread of viral infection on a global scale like that which happened in 1918.

12. Viruses with single-stranded RNA as their genome, and for which the base sequence of that RNA is the same as the viral mRNA are said to be ______viruses. A) minus-stranded B) mRNA-like C) plus-stranded D) reverse-transcribed

13. Viral genomes come in a variety of types. Which of the types of nucleic acids listed below are always present as part of a virus's genome?

A. ssRNA(-) B. ssDNA(+) C. ssRNA(+) D. dsDNA E. None of the above

14. Which of the following statements about H1N1 influenza are true? A) H1N1 is in circulation today B) The hemagglutin protein is identical to the neuraminidase protein because each is a subtype 1 C) The hemagglutin protein and the neuraminidase protein are encoded on RNA genome segment “1” in H1N1 D) Two of the above are correct E) A, B and C are correct

15. Consider the following bit of viral genome that is ssRNA(-): 5'-AUC CCG GUU AAA-3'. If you were going to figure out the sequence of the viral protein that is encoded by this bit of genome, your first job would be to figure out the proper codons. In this case, what are they?

A. 5'-AUC CCG UUG AAA-3' B. 5'-AAA UUG GCC CUA-3' C. 5'-UAG GGC CAA UUU-3' D. 5'-UUU AAC CGG GAU-3' E. None of the above, viruses with (-) genomes do not synthesize proteins. 16. Viruses that posses glycoprotein spikes acquire them A) as they exit the nuclear membrane of the host cell. B) as they exit the cell membrane of the host cell. C) during capsid assembly. D) in the cytoplasm of the host cell. E) Both a and b

19. Which of the diseases listed below is not a result of infection by a member of the Herpes family?

A. Cold sores B. Infectious mononucleosis C. Chicken pox D. Hepatitis E. All of the above are caused by Herpes viruses

20. HIV is a retrovirus, and many of the earliest anti-HIV drugs targeted reverse transcriptase. What does reverse transcriptase do?

A. Make DNA, using RNA as template B. Make ssRNA(+) using ssRNA(-) as a template C. Make ssRNA(-) using ssRNA(+) as a template D. Make RNA, using DNA as template E. Make dsDNA using ssDNA as a template

21. Imagine that a new form of influenza A was found where all 8 of the genome segments, that are normally found in influenza, were fused into one long genome. Which of the following statements about the new type of influenza would you expect to be true? A) The virus would be more variable because the RNA polymerase would be copying longer pieces of RNA B) The virus could undergo antigenic shift C) The virus could not undergo antigenic shift D) The virus would be more likely to undergo antigenic drift E) The virus would be less likely to undergo antigenic drift

22. In class we discussed viral hepatitis. Which statement about viral hepatitis is not true (or choose E if all are true).

A. It is always caused by enveloped viruses with RNA(+) genomes B. It is an infection of the liver C. It is can passed by blood or intimate contact D. It can be mild E. All of the above are true

23. New pandemic strains of influenza virus appear roughly every 20 to 30 years and cause disease that is much more severe than that caused by every winter by typical influenza viruses. The pandemic strains often differ from the usual influenza strains which of the following ways.

A. They are often hybrids of two viral subtypes B. They have RNA polymerases that are extremely accurate C. They have extra genome segments carrying extreme virulence genes D. Their N genes are missing and humans cannot mount an immune response to them E. Their H genes are missing, and humans cannot mount an immune response to them