Portage Microbiology Exam #6

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

Describe the two basic components of a virus (short answer)

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

The _____ surrounds the capsid of some viruses

Envelope

The envelope surrounds the _____ of some viruses

Capsid

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

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

False: Not all the viruses have envelopes

Rank the following viruses based on their size from largest to smallest: orthomyxovirus, poliovirus, variolavirus

Variolavirus>Orthomyxovirus>Poliovirus

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

Smallpox>Paramyxovirus>Poliovirus

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 or False: Highly infectious viruses undergo genome replication prior to viral attachment and entry.

False. The viral genome is never replicated before attachment and entry regardless of its level of infectivity.

Place the following viral life cycle steps in order beginning with viral attachment and provide a description of each step (short answer)

Uncoating: the viral capsid disassembles

Release: New virus particles are produced and leave the cell

Replication: the viral genome is the 'blueprint' to make copies of itself

Attachment: viral receptors bind to host proteins on the surface of the cell

Entry: the virus fuses with the host membrane and enters the cell

New Infection: newly produced viruses that left the host cell now go on to infect new cells

A virus that infects bacteria is called a _____ and contains a _____ -side polygon capsid (fill in the blank)

Bacteriophage; 20-sided

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

False. Bacteriophages have a distinct composition and structure

True or False. Structurally, bacteriophages are distinct from viruses that infect plant or animal cells.

True. Bacteriophages are structurally distinct from viruses that infect plant and animals cells.

Identify the following components of a bacteriophage (picture)

1. Capsid

2. Collar

3. Tail

4. Base

5. Tail fibers

Describe the main differences between lytic and temperate phages (short answer)

Lytic bacteriophages replicate within the host bacteria until it ruptures, whereas temperate 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

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

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 continues more and more bacterial cells will be destroyed, effectively clearing the media.

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.

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

True

True or False. A patient infected with Rubella is only considered infectious when the trademark rash is visible.

False. A patient infected with Rubella is infectious one week before and one week after the appearance of the rash.

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 linear, single-stranded RNA virus

What linear, double-stranded, enveloped DNA virus is the first virus (as of Oct. 26, 1977) to be officially declared eradicated? (short answer)

Smallpox

By whom and where was the first Polio vaccine developed?

Jonas Salk and his research team developed the polio vaccine at the University of Pittsburgh in 1955

What diseases displays as a secondary characteristic swelling of the testes/ovaries and pancreas? (short answer)

Mumps. They will have primary swelling in the parotid in the neck but will also have swelling in the testes/ovaries and pancreas

What disease is best characterized by painful swelling of the parotid? (short answer)

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

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

A. Impetigo

B. Conjuctivitis

C. Rheumatic fever

D. Influenza-like symptoms

B and D

You go to visit a friend who has chickenpox. While visiting what are two things you will be sure to avoid so 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 have to be absolutely certain to avoid direct contact with the blisters of an infected individual

True or False: Someone who had chicken pox 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 shingles reactivation and shingle diagnosis tends to occur in people greater than 60 years of age

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

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 chicken pox. Unvaccinated and unexposed individuals must first develop chickenpox, as shingles is the reactivation of the dormant VZV virus from the chickenpox infection

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.

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

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

Which subtype of Influenza is the most virulent?

Influenza A

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 hemagglutin proteins or nauraminidase proteins? Why?

Neuraminidase because it involves the budding and release of viral particles from the host cell

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 you took

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)

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

True

The HIV surface glycoprotein gp120 binds what host cellular receptor? (multiple choice)

D. CD4

The HIV surface glycoprotein gp41 binds what host cellular receptor? (multiple choice)

CXCR4

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

Anti-retrovirals are intended to inhibit the process of reverse-transcription. Once the virus enters the cell and uncoating is complete, the viral enzyme reverse transcriptase 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.