Week 6 Review Questions

20. True/False: An acute infection involves continuous release of virions for a long period of time

False, acute means short

28. True/False: Herpes simplex infections can be effectively treated/ cured.

False, there is no cure for Herpes. There are only suppressants to make symptoms less severe or decrease viral load

35. How is Hepatitis A transmitted?

Fecal/oral

45. Why are there more DNA viruses that cause cancer?

Humans have DNA that allows DNA viruses to integrate their chromosome into

18. What is one specific reason that susceptibility to a virus can vary from person to person?

Receptors on plasma membrane are different person to person so some people are more immunocompromised than others

21. What is the most common virus to cause the common cold?

Rhenovirus

46. What are oncolytic viruses?

Selectively infect & kill tumor/cancer cells by lysing. Many natural oncolytic viruses have been modified in research

19. What are the two ways that animal viruses can be released from a cell?

Most enveloped viruses released by budding Non enveloped viruses released by apoptosis

32. What effect do acyclovir/valacyclovir have on an active herpes infection?

Will not cure herpes Will suppress symptoms to make less severe

29. What can cause reactivation of herpes simplex virus?

physical/physiological stress, infection, fever, sunlight and menstruation

True/False: Viruses are acellular.

True

50. True/False: Prions are extremely resistant to many physical and chemical treatments.

True There is no cure for prion diseases

31. True/False: You MUST have been exposed to the varicella-zoster virus in order to have a shingles infection.

True, a person can only get Shingles if they have been exposed to Chickenpox (VZV)

30. What disease(s) does the varicella-zoster virus cause?

VZV causes Chickenpox and reactivation leads to latent infection Shingles (HZV)

25. What is a latent viral infection? Give an example.

Virus is maintained in a non-infectious state and produces more disease symptoms after re-activation Example is HSV (Herpes Simplex Virus) because HSV causes an acute infection that leads to symptoms of cold sores. From there, the virus can spread to sensory nerve cells where it remains latent. Later, the latent virus can reactivate to cause another episode of cold sores

Why did viral research start so much later than bacterial research? (History of viruses doesn't begin until late 1800's- why?)

Viruses can only multiply within living cells Viruses were too small to be seen with a light microscope that is used normally to observe bacterial cells. Viruses can only be seen with an electron microscope which was developed later. 1935, Wendell Stanley isolated TMV using an electron microscope Dimtri iwanoski filtered sap of diseased plants that were transmissible Martinus Bejernick worked with tobacco mosaic disease Viruses were distinguished from bacteria when passed through filters that retain bacteria

13. What are cytopathic effects? A. any detectable change in the host cell due to infection B. increase in number of infectious viruses C. antibody production during an infection D. none of the above

A. any detectable change in the host cell due to infection

48. What is the difference between the normal PrP protein (cellular) and the abrnormal PrP (scrapie)?

Abnormal proteins are not degraded by protease enzymes and kill the cell induces conversion of normal PrP into abnormal PrP that can cause neural brain damage (e.g. holes in brain tissue)

23. Which of the following is usually short in duration? Acute viral infection Chronic viral infection Latent viral infection None of the above

Acute infection

41. What term explains why you can get infected with influenza virus every year?

Antigenic drift - antigens mutate over time so virus mutates too not antigenic shift because antigenic shift is when a a sudden recombination of 2 or more strains of a virus occurs

38. What is the main receptor that HIV binds to on a human T cell?

B. CD4

43. Viruses capable of inducing tumors (cancer) in animals are called A. Lysogenic viruses B. Oncogenic viruses C. Transformed viruses D. none of the above

B. Oncogenic viruses

39. What is a provirus?

B. Viral DNA that is integrated into the animal host cell's DNA

10. Viruses that infect bacteria are called: A. satellites B. bacteriophages C. bacterioviruses D. bacteriocins

B. bacteriophages

4. Which of the following viral structures is composed entirely of proteins? A. genetic material B. capsid C. envelope D. spikes

B. capsid

6. Viruses are often measured in A. kilometers B. nanometers C. micrometers D. meters

B. nanometers

37. What unique enzyme do Retroviruses possess?

B. reverse transcriptase

34. How is Hepatitis C transmitted? Respiratory droplets Bodily fluids Fecal/oral None of the above

Bodily fluids (blood)

5. Glycoprotein projections that serve to attach viruses to a specific host cell are called: A. hooks B. cilia C. spikes D. pili

C. spikes

24. Which of the following involves continuous production of low levels of virus particles? Acute, chronic, latent or none of the these

Chronic Acute viral infection = burst of virions released from infected host cells Latent viral infection = virus remains silent within host re-activates to cause a productive infection. Some do not integrate into host cell chromosome & replicate in host chromosome

How is herpes simplex virus spread?

Contact

3. Which of the following is FALSE: A. Viruses are obligate intracellular parasites B. Viruses are not composed of cells C. Viruses can have either RNA or DNA as the genetic material D. Viruses don't have any nucleic acid; they must use the host cell genome.

D. Viruses don't have any nucleic acid; they must use the host cell genome.

7. Viral morphology can be describe using which term(s) A. helical B. polyhedral C. complex D. all of the above

D. all of the above

14. How does the synthesis of bacteriophage differ from animal viruses?

Differ in attachment or entry into the cell Differ in replication of viral nucleic acid Uncoating step is required by animal viruses Exits the host cell by budding/shedding

17. What are the two ways that animal viruses can enter (penetrate) a host cell?

Entry via membrane fusion - Spikes of virus attach to host receptors --> envelope of virion fuses with plasma membrane --> nucleocapsids is released into cytoplasm --> nucleic acid separates from capsid (uncoating) Entry via endocytosis - attachment to receptors triggers endocytosis --> plasma membrane surrounds the virus and forms a vesicle í envelope of virus fuses with the membrane --> nucleic acid separates from capsid (uncoating)

22. True/False: High numbers of viruses are required for the common cold to infect and cause symptoms.

False

42. Why does gene assortment occur so frequently in Influenza virus?

Gene assortment occurs frequently due to antigenic drift where antigens mutate over time, causing the virus to mutate too. We need new flu shots every year to target the new Influenza virus

40. How does HIV exit a T helper cell?

HIV is a retrovirus Infects WBCs called T helper cells by attaching to its CD4 receptors Fuses with host membrane Injects its genetic material into T cell Reverse transcriptase takes viral RNA from HIV to convert it to ssDNA and then synthesizes dsDNA Enzyme integrase allows HIV to integrate itself into our human DNA and establish lifelong infection with HIV

36. Which virus has an effective vaccine? (Circle all that apply) Hep A Hep B Hep C

Hep A and B Hep C does not have a vaccine

26. Which of the following best describes a Herpes simplex infection? Acute viral infection Chronic viral infection Latent viral infection None of the above

Latent viral infection because HSV reactivates to produce more cold sore symptoms

11. How are animal viruses grown in a lab?

Living animals, chick embryos & animal cell culture plaque assays detect phage particle concentration when phages infect & lyse inoculated bacterial cells on medium

9. What is a productive infection?

More new viral particles are produced

16. How do animal viruses attach to the host cell?

Spikes attach to specific receptors on the plasma membrane of the host cell Attachment site on non enveloped viruses are spikes on the capsid

12. What is a continuous cell line?

Transformed cancer cells that are maintained indefinitely and do not grow in monolayer in a lab

47. True/False: Prions are acellular

True

8. True/False: antiviral agents that damage the envelope (alcohols and detergents) reduce infectivity.

True

33. What can a chronic infection with Hepatitis B virus lead to?

liver cirrhosis & liver cancer

44. What is an oncogene?

mutated gene that has potential to cause cancer