Portage Learning BIOD 171 Module 6
Exam Module 6
1. True or False. Because the genome is contained within an enclosed space, (much like the nucleus of a
... [Show More] cell) viruses are classified as eukaryotic.
False. Viruses are neither eukaryotic nor prokaryotic.
2. Describe the two basic components of a virus.
A virus has (1) genomic material comprised of either DNA or RNA and (2) a capsid, a membrane-like protective structure that contains the genetic material, similar to the nucleus of a eukaryotic cell.
3. The………………surrounds the capsid of some viruses.
Envelope.
4. True or False. You would expect to see a viral envelope on a virus infecting a plant cell.
False. The overwhelming majority of animal viruses are enveloped whereas the majority of plant or bacteria-infecting viruses are not.
5. Rank the following viruses based on their size from largest to smallest:
Orthomyxovirus
Poliovirus
Variolavirus
Variolavirus (~200nm) > Orthomyxovirus (100-150nm) > Poliovirus (~30nm)
6. True or False: Viral replication occurs after it attaches and enters the host cell. True. The viral genome is never replicated before attachment and entry.
True. The viral genome is never replicated before attachment and entry.
7. Place the following viral life cycle steps in order beginning with viral attachment and provide a description of each step.
Uncoating:
Release:
Replication:
Attachment:
Entry:
New infection:
3- Uncoating: the viral capsid disassembles
5-Release: New virus particles are produced and leave the cell
4-Replication: the viral genome is the ‘blueprint’ to make copies of itself
1-Attachment: viral receptors bind to host proteins on the surface of the cell 2-Entry: the virus fuses with the host membrane and enters the cell
6-New infection: newly produced viruses that left the host cell now go on to infect new cells.
8. A virus that infects bacteria is called a…….and contains a……..-side polygon capsid.
Bacteriophage; 20-sided
9. True or False. Structurally, bacteriophages are similar to viruses that infect animals.
False. Bacteriophages have a distinct composition and structure.
10. Identify the following components of a bacteriophage.
1-Capsid (or Head)
2-Collar
3-Tail (sheath)
4-Base plate
5-Tail fibers
11. Describe the main differences between lytic and temperate phages.
Lytic bacteriophages replicate within the host bacteria until it ruptures, whereas temporate (or lysogenic) phages primarily exist in a non-replicative state that does not kill the host cell.
Lytic phages replicate all viral proteins needed for the assembly of new virus particles whereas lysogenic phage genomes are integrated into the host genome but production of viral proteins is suppressed.
12. Based on the following image, would you expect the viral titer to be high or low?
Low. As turbidity is a function of the number of intact bacterial cells present in the media, the amount of virus contained within the above tube must be low. As the lytic cycle continues more and more bacterial cells will be destroyed, effectively clearing the media.
13. Which of the following cannot be spread via airborne particles:
A. Measles
B. Mumps
C. Rubella
D. A and B
E. None of the above
E. Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc.
14. True or False. A patient infected with Rubella is considered infectious one week before and after the appearance of the trademark rash.
True
15. Which of the following diseases does a linear, double-stranded DNA virus cause?
A. Measles
B. Mumps
C. Rubella
D. B and C
E. None of the above
E. Measles, mumps and rubella are all linear, single-stranded RNA viruses
16. What disease displays as a secondary characteristic swelling of the testes/ovaries and pancreas?
Mumps. A patient infected with mumps (aka epidemic parotitis) has primary swelling in the parotid (salivary glands) located in the neck but also may have secondary swelling in the testes/ovaries and pancreas.
17. A patient diagnosed with German measles may additionally experience what disease? Select all that apply.
A. Impetigo
B. Conjunctivitis
C. Rheumatic fever
D. Influenza-like symptoms
B and D. A patient may experience a combination of symptoms such as fever, flu-like symptoms (influenza), cough, conjuctivitis, and a red blotchy skin rash.
18. You go to visit a friend who has chickenpox. While visiting what are 2 things you will be sure to avoid so that you don’t also become infected?
(1) You would want to be sure to keep a distance especially if your friend is coughing or sneezing as chickenpox can be transmitted through air-borne droplets (sneezing/coughs). (2) You would also be absolutely certain to avoid direct contact with the blisters of an infected individual.
19. True or False. Someone who had chickenpox as a child is likely to develop shingles while in college, where the median age of college students is 18-22 years old.
False. The most common age for VZV reactivation and shingle diagnosis tends to occur in people greater than 60 years of age.
20. True or False. Similar to chickenpox, the blisters that appear with Shingles can cover the entire body.
False. Unlike chickenpox blisters, which can form anywhere, the blisters associated with shingles are localized and limited to small areas.
21. A person who has neither previously had chickenpox nor been administered the VZV vaccine is exposed to someone with an active VZV (shingles) outbreak and becomes infected. Explain why (or why not) the person will only develop shingles.
The infected individual will not develop shingles, but will develop chickenpox. Unvaccinated and unexposed individuals must first develop chickenpox, as shingles is the reactivation of the dormant VZV virus from the chickenpox infection.
22. While traveling abroad, should you be worried about coming into contact with either the Variola major or Variola minor viruses?
No. Both viruses are variants of smallpox and were eradicated in 1977. You would not need to worry about coming into contact with the virus.
23. What small (~30nm) single-stranded, non-enveloped RNA virus causes temporary or permanent paralysis by infiltrating (infecting) motor neurons within the spinal cord, brain stem or motor cortex?
Polio, also known as poliomyelitis.
24. Described the main underlining differences between the Salk and Sabin polio vaccine.
The Salk vaccine contained an inactivated form of the virus and was injected while the Sabin vaccine contained a live attenuated (weakened) form of the virus and was administered orally.
25. Which subtype of Influenza is the most virulent?
Influenza A
26. A drug company is trying to develop a new drug that will inhibit the release of newly produced viral particles. Would the drug company target hemagglutinin proteins or neuraminidase proteins? Why?
Neuraminidase because it involves the budding & release of viral particles from the host cell
27. Explain why the flu shot given each year may not be 100% effective at preventing the flu?
Because you may be exposed to a viral strain that is not included in the making of the vaccine of the flu shot that you took.
28. A drug company is trying to develop a new drug that will inhibit the release of newly produced viral particles. Would the drug company target hemagglutinin proteins or neuraminidase proteins? Why?
Neuraminidase (N) proteins are directly involved in the budding and release of new viral particles and would thus be the correct target. Hemagglutinin (HA) proteins would not be advisable targets as they are directly involved in viral attachment and entry into the host cell.
29. Explain why the flu shot given each year may not be 100% effective at preventing the flu?
It is possible to receive a flu vaccine and yet (unfortunately) still get the flu in the same season if you are exposed to a viral strain that was not included in the vaccine. There are a large number of variants and the flu vaccine is unable to vaccinate against all subtypes.
Medical researchers predict and then distribute flu vaccines based current trends and the available data relative to the most common circulating strains. Unfortunately, this model is not always 100% accurate.
Once HIV enters the cell, the capsid is degraded, & the HIV protein reverses transcription & makes 2 RNA copies, generating DNA strand which is then transported into the nucleus where it integrates the host genome. The virus is then replicated & new viruses are formed. Anti-retroviral medication helps to fight the ability of the virus to reproduce
30. True or False. The viral capsid of HIV is dumbbell shaped and contains ~2,000 copies of the viral protein p24.
False. The HIV capsid is conical (cone) shaped.
31. The HIV surface glycoprotein gp120 binds what host cellular receptor?
A. CD3
B. CXCR4
C. CCR5
D. CD4
D. HIV gp120 binds to CD4.
32. An individual infected with HIV is placed on anti-retroviral medication. Describe how the medication will affect the virus.
As the name suggests, anti-retrovirals are intended to inhibit (anti) the process of reverse- transcription (retro). Once the virus enters the cell and uncoating is complete, the viral enzyme reverse transcriptase (RT) acts on the two RNA copies, creating a complementary DNA strand. Anti-retrovirals attempt to block this step. In the absence of anti-retroviral medications, the now double-stranded DNA is transported to the nucleus where it can integrate into the host genome and begin replicating. By inhibiting the process of RT, anti- retroviral medications effectively block the production of new viruses by preventing its integration and replication. [Show Less]