Mod 6 Test

Question 1

True or False. Although viruses may contain their genome within an enclosed space (much like the nucleus of a cell), it is considered neither eukaryotic nor prokaryotic.

Answer 1

True

Question 2

Describe the two basic components of a virus.

Answer 2

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.

Question 3

The envelope surrounds the _________ of some viruses.

Answer 3

Capsid

Question 4

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

Answer 4

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

Question 5

Rank the following viruses based on their size from largest to smallest:

Orthomyxovirus

Poliovirus

Variolavirus

Answer 5

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

Question 6

True or False: Viral replication occurs after it attaches and enters the host cell.

Answer 6

True
True. The viral genome is never replicated before attachment and entry.

Question 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:

Answer 7

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.

Question 8

A virus that infects bacteria is called a [answer1] and contains a [answer2] -sided polygon capsid.

Answer 8

1. Bacteriophage
2. 20

Question 9

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

Answer 9

False
False. Bacteriophages have a distinct composition and structure.

Question 10

Identify the following components of a bacteriophage.
1-[answer1]

2- [answer2]

3- [answer3]

4- [answer4]

5- [answer5]

Answer 10

1. Capsid
2. Collar
3. Helical Tail(Shaft)
4. Baseplate
5. Tail Fibers

Question 11

Describe the main differences between lytic and temperate phages.

Answer 11

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.

Question 12

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

Answer 12

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.

Question 13

Which of the following cannot be spread via airborne particles:

Answer 13

None of the above
Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc.

Question 14

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

Answer 14

True

Question 15

A patient diagnosed with German measles may additionally experience what disease? Select all that apply.
Impetigo
Conjunctivitis
Rheumatic fever
Influenza-like symptoms

Answer 15

Conjunctivitis
Influenza-like symptoms

A patient may experience a combination of symptoms such as fever, flu-like symptoms (influenza), cough, conjuctivitis, and a red blotchy skin rash.

Question 16

Which of the following diseases does a linear, single-stranded RNA virus cause?
Measles
Mumps
Rubella
B and C
All of the above

Answer 16

All of the above

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

Question 17

What disease is best characterized by painful swelling of the paratoid?

Answer 17

Mumps. A patient infected with mumps (aka epidemic paratitis) has swelling in the paratoid (salivary glands) located in the neck.

Question 18

Describe two ways chickenpox can be spread.

Answer 18

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.

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 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.

Answer 21

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.

Question 22

While traveling abroad, should you be worried about coming into contact with either the Variola major or Variola minor viruses?

Answer 22

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.

Question 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?

Answer 23

Polio, also known as poliomyelitis.

Question 24

Describe the main underlining differences between the Salk and Sabin polio vaccine.

Answer 24

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.

Question 25

Which subtype of Influenza is the most virulent?

Answer 25

Influenza A

Question 26

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?

Answer 26

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.

Question 27

Explain why the flu shot given each year may not be 100% effective at preventing the flu?

Answer 27

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.

Question 28

True or False. The viral capsid of HIV is cone shaped and contains ~2,000 copies of the viral protein p24.

Answer 28

True

Question 29

The HIV surface glycoprotein gp41 binds what host cellular receptor?

Answer 29

CXCR4
HIV gp41 binds to the receptor CXCR4

Question 30

An individual infected with HIV is placed on anti-retroviral medication. What is the general purpose of this medication?

Answer 30

As the name suggests, anti-retrovirals are intended to inhibit (anti) the life cycle of retroviruses (retro). By inhibiting steps in the HIV’s lifecycle, anti-retroviral medications effectively block the production of new virus particles and lower the viral load of the patient.