Microbiology- exam 6

Identify the following components of a bacteriophage.

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

Place the following viral life cycle steps in order beginning with viral attachment and provide a description of each step.

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.

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

The HIV surface glycoprotein gp120 binds what host cellular receptor?

A. CD3 B. CXCR4 C. CCR5 D. CD4 D. HIV gp120 binds to CD4.

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.

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

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

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.

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

Bacteriophage; 20-sided

The envelope surrounds the _________ of some viruses.

Capsid

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

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

False. Bacteriophages have a distinct composition and structure.

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. 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.

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

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.

Which subtype of Influenza is the most virulent?

Influenza A

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.

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. 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

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.

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.

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

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

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

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.

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. 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.

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.

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