M 6 exam

1. 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.

3. Identify the following components of a bacteriophage.

1-Capsid (or Head), 2-Collar, 3-Tail (sheath), 4-Base plate, 5-Tail fibers

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.

5. A patient diagnosed with German measles may additionally experience what disease? Select all that apply.

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.

1. A virus that infects bacteria is called a ____________ and contains a _____-side polygon capsid.

Bacteriophage; 20-sided

2. 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.

1. The envelope surrounds the _________ of some viruses.

Capsid.

1. Describe two ways chickenpox can be spread.

Chickenpox is highly contagious and can be transmitted (1) through both air-borne droplets (sneezing/coughs) or via (2) direct contact with the blisters of an infected individual.

2. The HIV surface glycoprotein gp120 binds what host cellular receptor?

D. HIV gp120 binds to CD4.

3. Which of the following diseases does a linear, double-stranded DNA virus cause?

E. Measles, mumps and rubella are all linear, single-stranded RNA viruses

3. 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

1. Which of the following cannot be spread via airborne particles:

E. Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc.

1. 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.

1. The ________ surrounds the capsid of some viruses.

Envelope.

2. True or False. Structurally, bacteriophages are similar to viruses that infect animals.

False. Bacteriophages have a distinct composition and structure.

1. 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.

2. 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.

2. True or False. You would expect to see a viral envelope on a virus infecting a bacterial cell.

False. The overwhelming majority of animal viruses are enveloped whereas the majority of plant or bacteria-infecting viruses are not.

2. 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.

3. 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.

1. True or False. Because the genome is contained within an enclosed space, (much like the nucleus of a cell) viruses are classified as eukaryotic.

False. Viruses are neither eukaryotic nor prokaryotic.

True or False. Because the genome is contained within an enclosed space, (much like the nucleus of a cell) viruses are classified as eukaryotic.

False. Viruses are neither eukaryotic nor prokaryotic.

1. A drug company is trying to develop a new drug that will inhibit viral entry of Influenza. Would the drug company target hemagglutinin proteins or neuraminidase proteins? Why?

Hemagglutinin (HA) proteins would be targets as they are directly involved in viral attachment and entry into the host cell. Neuraminidase proteins are involved in the budding and release of new viral particles and would thus not be the correct target.

4. Which subtype of Influenza is the most virulent?

Influenza A

2. 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 still get the flu in the same season if you are exposed to a viral strain that was not included in the vaccine. Medical researchers predict, then distribute flu vaccines, this model is not always 100% accurate.

2. Based on the following image, would you expect the viral titer to be high or low? Why?

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.

1. 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.

4. 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.

1. 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.

1. 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

New infection:

New viruses produced leaves the host cell & go infect new cells. This process restarts

1. 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.

Exit:

Old virus leaves the cell & new viruses are produced

2. 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.

3. Rank the following viruses based on their size from largest to smallest: Paramyxovirus Poliovirus Smallpox virus

Smallpox (~200nm) > Paramyxovirus (100-150nm) > Poliovirus (~30nm)

3. 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.

4. 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.

Uncoating:

The viral capsid is pulled apart where applicable.

Replication:

The viral genome makes copies of itself

Entry:

The virus joins with the membrane of host & enters cell

Attachment:

The virus receptors binds to the host protein outside the cell

2. True or False. A patient infected with Rubella is considered infectious one week before and after the appearance of the trademark rash.

True

2. True or False. The development of shingles is most often seen in an older adult population (> 60 years old).

True. The most common age for VZV reactivation and shingle diagnosis tends to occur in people around 60 years of age.

1. 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.

3. True or False. Unlike chickenpox, the blisters that appear with shingles are localized and limited to small areas.

True. While chickenpox blisters often cover the entire body, the blisters associated with shingles are localized and limited to small areas.

2. 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. Rank the following viruses based on their size from largest to smallest: Orthomyxovirus, Poliovirus, Variolavirus

Variolavirus (~200nm) > Orthomyxovirus (100-150nm) > Poliovirus (~30nm)

3. An individual infected with HIV is placed on anti-retroviral medication. Describe how the medication will affect the virus.

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.