Module 6 Test
Identify the following components of a bacteriophage.
1-Capsid 2- Collar 3- Tail 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 Uncoating: Release: Replication: Attachment: Entry: New infection:
ANSWER: 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.
You go to visit a friend who has chickenpox. While visiting what are 2 things you will be sure to avoid it so that you don't also become infected?
ANSWER: (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.
Describe the two basic components of a virus.
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.
Which of the following CAN be spread via airborne particles: A. Measles B. Mumps C. Rubella D. A and B E. All of the above
ANSWER: ALL 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, single-stranded RNA virus cause? A. Measles B. Mumps C. Rubella D. A and B E. All of the above
ANSWER: All of the above. Measles, mumps and rubella are all linear, single-stranded RNA viruses.
An individual infected with HIV is placed on anti-retroviral medication. What is the general purpose of this medication?
ANSWER: As the name suggests, anti-retrovirals are intended to inhibit (anti) the life cycle of retroviruses (retro). By inhibiting steps in the HIV's life cycle, anti-retroviral medications effectively block the production of new virus particles and lower the viral load of the patient.
The envelope surrounds the ______ of some viruses.
ANSWER: Capsid
A patient diagnosed with German measles may additionally experience what disease? Select all that apply. A. Impentigo B. Conjunctivitis C. Rheumatic fever D. Influenza-like symptoms
ANSWER: Conjunctivitis; Influenza-like symptoms. A patient may experience a combination of symptoms such as fever, flu-like symptoms (influenza), cough, conjunctivitis, and a red blotchy skin rash.
The ________ surrounds the capsid of some viruses.
ANSWER: Envelope
True or False. A patient infected with rubella is only considered infectious when the trademark rash is visible.
ANSWER: False. A patient infected with Rubella is infectious one week before and one week after the appearance of the rash.
True or False. Structurally, bacteriophages are similar to viruses that infect animals.
ANSWER: 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.
ANSWER: 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.
ANSWER: 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 plant cell.
ANSWER: False. The overwhelming majority of animal viruses are enveloped whereas the majority of plant or bacteria-infecting viruses are not.
True or False. Similar to chickenpox, the blisters that appear with shingles can cover the entire body.
ANSWER: False. Unlike chickenpox blisters, which can form anywhere, the blisters associated with shingles are localized and limited to small areas.
True or False. Because the genome is contained within an enclosed space (much like the nucleus of a cell), viruses are classified as eukaryotic.
ANSWER: False. Viruses are neither eukaryotic nor prokaryotic.
The HIV surface glycoprotein gp120 binds what host cellular receptor? A. CD4 B. CXCR4 C. HIV gp41 binds to the receptor CXCR4 D. CD3 E. CXCR5
ANSWER: HIV gp120 binds to CD4.
The HIV surface glycoprotein gp41 binds what host cellular receptor? A. CD4 B. CXCR4 C. HIV gp41 binds to the receptor CXCR4 D. CD3 E. CXCR5
ANSWER: HIV gp41 binds to the receptor CXCR4
A virus that infects bacteria is called a [answer1] and contains a [answer2] -sided polygon capsid.
ANSWER: [answer 1] Bacteriophage; [answer 2] 20
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: 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?
ANSWER: Influenza A
Explain why the flu shot given each year may not be 100% effective at preventing the flu?
ANSWER: 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 on 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?
ANSWER: 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.
Describe the main differences between lytic and temperate phages.
ANSWER: 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?
ANSWER: Mumps. A patient infected with mumps (aka epidemic paratitis) has primary swelling in the paratoid (salivary glands) located in the neck but also may have secondary swelling in the testes/ovaries and pancreas.
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
ANSWER: NONE OF THE ABOVE. Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc.
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?
ANSWER: Neuraminidase (N) proteins are 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.
While traveling abroad, should you be worried about coming into contact with either the Variola major or Variola minor viruses?
ANSWER: 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.
Which of the following diseases does a linear, single-stranded DNA virus cause? A. Measles B. Mumps C. Rubella D. A and B E. None of the above
ANSWER: None of the above. Measles, mumps and rubella are all linear, single-stranded RNA viruses.
What small (~30nm) single-stranded, non-enveloped RNA virus targets the CNS (central nervous system), causing potentially catastrophic damage to motor neurons? ALTERNATE WORDING: 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: Polio, also known as poliomyelitis.
What linear, double-stranded, enveloped DNA virus is the first virus (as of Oct. 26, 1977) to be officially declared eradicated?
ANSWER: Smallpox (Variola virus). Although once a major cause of death in the world, a smallpox vaccine was developed in 1796 by Edward Jenner. Global vaccination efforts have prevented smallpox from appearing in humans since October 26, 1977, making smallpox the first infectious disease ever to be eradicated.
Describe the main underlying differences between the Salk and Sabin polio vaccine.
ANSWER: 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.
ANSWER: 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. 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: True
True or False. Unlike chickenpox blisters, which can form anywhere, the blisters associated with shingles are localized and limited to small areas.
ANSWER: True
True or False. A patient infected with Rubella is infectious one week before and one week after the appearance of the rash.
ANSWER: True.
True or False. The viral capsid of HIV is cone shaped and contains ~2,000 copies of the viral protein p24.
ANSWER: True. The HIV capsid is conical (cone) shaped.
True or False. The development of shingles is most often seen in an older adult population (> 60 years old).
ANSWER: 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.
ANSWER: True. The viral genome is never replicated before attachment and entry.
Rank the following viruses based on their size from largest to smallest: Orthomyxovirus Poliovirus Variolavirus
ANSWER: Variolavirus (~200nm) > Orthomyxovirus (100-150nm) > Poliovirus (~30nm)
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.