Microbiology Chapter 13
Bovine Spongiform Encephalopathy is also known as ___________?
"mad cow disease"
What are the there types of RNA viruses?
+ssRNA -ssRNA dsRNA
What is a virus?
A minuscule, acellular, infectious agent having either DNA or RNA
A virion without an envelope is a (blank) virion.
A nonenveloped virion or naked virion.
What is the viral envelope?
A portion of the membrane system of the host that is composed of a phospholipid bilayer and proteins (typically have glyoproteins)
What is Direct Penetration?
A process where naked virions inject their genomes into their animal cell hosts
What is the extracellular state of a virus called?
A virion
How is the viral envelope acquired?
Acquired from host cell during viral replication or release.
A virion with a membrane is a (blank) virion.
An enveloped virion.
If animal viruses are not mobile, how do they attach?
Animal viruses have glycoprotein spikes or other attachment molecules that mediate attachment.
What is Endocytosis?
Attachment of a naked or an enveloped virus stimulates the host cell to engulf the virus.
What are the five stages of lytic replication? Describe each.
Attachment- of virion to host cell Entry- of virion or its genome into host cell Synthesis- of new nucleic acids and viral proteins by host cells enzymes and ribosomes Assembly- of new virions within host cells Release- of new virions from host cell
How is mRNA synthesized in -ssRNA?
By RNA-dependent RNA transcriptase. -ssRNA is able to synthesize mRNA by RNA-dependent RNA transcriptase.
What is cellular PrP?
Cellular PrP is made by all mammals and has a normal, functional structure with alpha-helices
What is Membrane Fusion?
Fusion of the viral envelope and cell membrane dumps the capsid into the cell.
What are generalist viruses?
Generalists infect many kinds of cells or many different hosts.
Give an example of a virus that may be so specific they only infect particular kind of cell in a particular host.
HIV specifically attacks T lymphocytes, has no impact on muscle
What are the three basic type of viral shapes?
Helical Polyhedral Complex
What is the exception to how dsDNA animal viruses replicate? How?
Hepatitis B Hepatitis B viruses replicate DNA from an RNA intermediary.
A modified replication in which infected host cells grow and reproduce normally for many generations before they lyse. This is called lysogency or (blank) replication
Lysogenic
In (blank) replication, infected host cells grow and reproduce normally for generations before they lyse.
Lysogenic Replication.
The replication cycle of a virus usually results in death and lysis of a cell. Due to it undergoing lysis near the end of the cell, it is called (blank) replication.
Lytic
The following statement describes which of the following- lytic or lysogenic replication? Viral replication usually results in death and lysis of the host cell.
Lytic Replication
What is the complex shape composed of?
Many different shapes that do not readily fit into either of the other two categories.
Give two examples of viruses with a complex shape.
Megavirus and Rabies Virus
Why are enveloped viruses more fragile than naked viruses outside the host?
Membranes provide some protection but are more susceptible to detergents, alcohol, and drying out so enveloped viruses are more fragile than naked.
What are the three main types of host characteristics of viruses?
Most viruses infect only particular host's cell May be so specific they only infect particular kind of cell in a particular host Generalists infect many kinds of cells or many different hosts
Negative sense viral RNA cannot be directly translated so it must be copied to positive sense viral RNA before protein synthesis.
Negative sense viral RNA cannot be directly translated so it must be copied to positive sense viral RNA before protein synthesis.
What must - RNA undergo before it can carry out protein synthesis?
Negative sense viral RNA cannot be directly translated. It must be copied to positive sense before protein synthesis.
What nucleic acids do prions use?
None
Viriods are extremely small, circular pieces of ssRNA that are infections and pathogenic in ____________?
Plants
Positive sense viral RNA can act as mRNA.
Positive sense viral RNA can act as mRNA.
How is mRNA synthesized in dsRNA?
Positive strang of genome acts as mRNA dsRNA is able to synthesize mRNA by a positive strand of the genome acting as mRNA.
Differences in animal viruses result from what three major things?
Presence of envelope and some viruses Eukaryotic nature of animal cells Lack of cell wall in animal cells
What PrP is the disease causing form?
Prion PrP
What is prion PrP?
Prion PrP is disease causing and has beta sheets. It is anchored in lipid rafts which play a role in normal brain activity.
Which of the following does not use any nucleic acids? Viruses Viroids Prions Bacteria
Prions do NOT use any nucleic acids. Viruses use either DNA or RNA but never both, Viroids use RNA only, and Bacteria uses DNA and RNA
What are prions?
Proteinaceous infectious particles that lack nucleic acids and replicate by converting similar normal proteins into new prions
What nucleic acids do viroids use?
RNA only
What is the main difference between ssDNA and dsDNA regarding how mRNA is synthesized?
RNA polymerase location In ssDNA, the RNA polymerase is ONLY found in the nucleus of a cell. In dsDNA, the RNA polymerase can be found EITHER the nucleus or cytoplasm of a cell.
In the synthesis of DNA and RNA viruses of animals, DNA viruses often enter the nucleus while RNA viruses often (blank) in the cytoplasm.
Replicate. In the synthesis of DNA and RNA viruses of animals, DNA viruses often enter the nucleus while RNA viruses often replicate in the cytoplasm.
Give an example of a virus with a polyhedral shape.
Rhinovirus (common cold)
Most RNA animal viruses (blank) in the cytoplasm.
develop
Describe the templating action of prions
1) Cells make c-PrP which is inserted into the cytoplasmic membrane 2) p-PrP may infect the brain or may be produced by an altered c-PrP gene 3) Prion protein (p-PrP) reacts with c-PrP on the cell surface 4) p-PrP converts c-PrP to p-PrP 5) The new p-PrP converts more c-PrP
What is the purpose of a capsid?
A capsid provides protection of viral nucleic acid and is a means of attachment to host's cells
What are some animal viruses that may remain dormant for periods of time (latency)
AIDS, chicken pox, hepatitis B, herpes
Which of the following has a cytoplasmic membrane? Viruses Viroids Prions Bacteria
Bacteria In Viruses, Viroids, and Prions their cytoplasmic membrane is absent. Although, some viruses do have a membranous envelope.
Which of the following has functional ribosomes? Viruses Viroids Prions Bacteria
Bacteria In Viruses, Viroids, and Prions there are not functional ribosomes.
What nucleic acids do bacteria use?
Both DNA and RNA
The rabies virus has a complex shape, what shape is it?
Bullet shaped.
How is mRNA synthesized in ssDNA?
By RNA polymerase (in the nucleus of a cell) In ssDNA, mRNA is synthesized by RNA polymerase which is found in the nucleus of a cell.
How is mRNA synthesized in dsDNA?
By RNA polymerase (in the nucleus or cytoplasm of a cell) In dsDNA, mRNA is synthesized by RNA polymerase which is found in the nucleus or cytoplasm of a cell.
What is the extracellular state of a virus?
Called a vision. Protein coat (capsid) surging the nucleic acid. The nucleic acid and capsid are called the nucleocapsid Some have a phospolipid bilayer surrounding the nucleocapsid Outerlayer provides protection and recognition sites for hosts cell
Once a virus is inside a cell, the intracellular state is initiated and the (blank) is removed.
Capsid
What is the intracellular state of a virus?
Capsid removed Virus exists as nucleic acid interacting with viral and host proteins
The mega virus has a complex shape, what shape is it?
Capsid shape.
What is the helical shape composed of?
Composed of capsomeres that bond together in circling fashion to form a tube around the nucleic acid
What are capsids composed of?
Composed of proteinaceous subunits called capsomeres.
In dsRNA viruses of animals, viral genome is replicated in the nucleus and viral proteins are made in the (blank).
Cytoplasm In dsRNA viruses of animals, viral genome is replicated in the nucleus and viral proteins are made in the cytoplasm.
How is mRNA synthesized in +ssRNA (Retroviridae)?
DNA is synthesized from RNA by reverse transcriptase; mRNA is transcribed from DNA by RNA polymerase. RNA synthesized in +ssRNA (Retroviridae) by the synthesis of DNA from RNA by reverse transcriptase; mRNA is transcribed from DNA by RNA polymerase.
What are the three mechanisms of entry of animal viruses?
Direct Penetration Membrane Fusion Endocytosis
Why is it that some viruses only infect particular host's cells?
Due to the affinity of viral surface proteins for complementary proteins on host cell surface
True or False? Viral genera cannot be organized into families.
False. Viral genera have only been organized into families.
True or False? Only some organisms are susceptible to some virus.
False. All types of organisms are susceptible to some virus.
True or False? Animal viruses are mobile?
False. Animal viruses do not have tails or tail fibers.
What nucleic acids do viruses use?
Either DNA or RNA but NEVER both
True or False? Normal sterilization procedures deactivate prions.
FALSE. Normal sterilization procedures DO NOT deactivate prions.
True or False? Viruses can contain both DNA and RNA.
FALSE. Viruses may contain DNA or RNA but NEVER both.
True or False? Each type of animal virus requires the same strategy for replication.
False. Each type of animal virus requires a different strategy depending on its nucleic acid
True or False? Incorporation of provirus into host cell is temporary.
False. Incorporation of provirus into host cell is permanent.
True or False? A virus can grow and respond to an environment as well as reproduce independently.
False. A virus CANNOT grow or respond to the environment. It also CANNOT reproduce independently.
True or False? Capsomeres can only be made of single types of proteins.
False. Capsomeres may be made of single or multiple types of proteins.
True or False? Enveloped viruses acquire their enveloped from the hosts before viral replication or release.
False. Enveloped viruses acquire their enveloped from the hosts DURING viral replication or release.
True or False? The envelope proteins and glycoproteins often play no role in host recognition.
False. The envelope proteins and glycoproteins often play a role in host recognition.
What can prions be destroyed by?
Incineration or autoclaving in concentrated sodium hydroxide
Which of the following is NOT an animal prion disease? Scrappie Transmissable Mink Encephalopathy Chronic Wasting Disease Kuru Bovine Spongiform Encephalopathy
Kuru is NOT an animal prion disease. Kuru is a human prion disease. Animal prion diseases are: Scrappie Transmissable Mink Encephalopathy Chronic Wasting Disease Bovine Spongiform Encephalopathy ("mad cow disease")
What is the term used to describe when animal viruses remain dormant in host cells?
Latency
What is the polyhedral shape composed of?
Roughly spherical shape similar to a geodesic dome.
Which of the following is NOT a human prion disease? Creutzfeldt-Jakob disease Scrapie Gerstmann-Straussler-Scheinker syndrome Fatal Familial Insomnia Kuru
Scrapie is NOT a human prion disease. Scrapie is an animal prion disease. Human prion diseases are: Creutzfeldt-Jakob disease Gerstmann-Straussler-Scheinker syndrome Fatal Familial Insomnia Kuru
Characterize the genetic material of viruses
Show more variety in nature of their genomes than cells May be DNA or RNA but NEVER both May be linear and segmented or single and circular Much smaller than genomes of cells
Synthesis of RNA viruses differs from DNA virus replication.Viral RNA- dependent RNA polymerase (RdRp) is required so it must be made first or brought along. Positive sense viral RNA can act as mRNA. Negative sense viral RNA cannot be directly translated so it must be copied to positive sense viral RNA before protein synthesis.
Synthesis of RNA viruses differs from DNA virus replication.Viral RNA- dependent RNA polymerase (RdRp) is required so it must be made first or brought along. Positive sense viral RNA can act as mRNA. Negative sense viral RNA cannot be directly translated so it must be copied to positive sense viral RNA before protein synthesis.
How is mRNA synthesized in +ssRNA?
The genome acts as mRNA mRNA synthesized in +ssRNA is achieved by the genome acting as mRNA.
The outermost layer of the extracellular state provides what? (2)
The outermost layer provides protection and recognition sites for host cells
What is a capsid?
The protein coat surrounding the nucleic acid in the extracellular state of a virus
Animal Viruses- The number of viruses produced depends on what three things?
The type of virus, size, and initial health of host cell. The number of viruses produced depends on the type of virus, size, and initial health the host cell.
All viruses lack cell membranes because why?
They are not cells! HOWEVER, some viruses have an envelope (mainly animal cells)
There are how many basic types of viral shapes?
Three
Give an example of a virus with a helical shape.
Tobacco Mosaic Virus
True or False? Lysogenic replication is a modified replication cycle.
True
True or False? Some animal viruses may be prolonged for years with no viral activity.
True.
True or False? Viroids lack capsids.
True.
True or False? A virion has both an extracellular and intracellular state.
True.
True or False? Prion PrP causes cellular PrP to refold into prion PrP
True.
True or False? The glycoproteins of the viral envelope are often spiked and virally coded.
True.
True or False? dsRNA animal viruses are similar in replication to cellular DNA.
True.
True or False? Cells do not use ssDNA.
True. Parvoviruses have ssDNA genomes. DNA strand folds back on itself to form dsDNA which is replicated by cellular DNA polymerase.
True or False? A virus cannot carry out any metabolic pathway.
True. Instead, once a virus has invaded a cell, it will take control of the cell's metabolism. In doing this, it will produce more molecules of viral nucleic acids and proteins.
True or False? Viruses without a capsid exist solely as a nucleic acid but are still called a virus.
True. Viruses without a capsid exist solely as a nucleic acid but are still called a virus.
True or False? Enveloped viruses are more fragile than naked viruses outside the host cell.
True. Enveloped viruses are more fragile than naked viruses outside host.
True or False? Naked viruses are more stable than enveloped viruses outside the host but exposed viral proteins make them more susceptible.
True. Exposed viral proteins to the environment makes naked viruses more susceptible to recognition.
True or False? Negative sense viral RNA cannot be directly translated.
True. Negative sense viral RNA cannot be directly translated. It must be copied to positive sense before protein synthesis.
True or False? Viriods and Prions are examples of parasitic particles.
True. Virions and Prions are examples of parasitic particles.
Viral classification is based on what four things?
Type of Nucleic Acid Presence of an Envelope Shape Size
Retroviruses do not use their genomes as mRNA. Instead, they use a DNA intermediary transcribed by viral revere transcriptase as a template to produce (blank).
Viral Genomes. Retroviruses do not use their genomes as mRNA. Instead, they use a DNA intermediary transcribed by viral revere transcriptase as a template to produce viral genomes.
What makes up a nucleocapsid?
Viral nucleic acid + capsid = nucleocapsid
What is a nucleocapsid?
Viral nucleic acid and capsid
Viruses can be classified by (blank) shape.
Virion. Viruses can be classified by virion shape.
Viruses can be linear and (blank) or singular and (blank).
Viruses can be linear and segmented or single and circular.
Viruses in extracellular state have virions have capsids which are protein coats that provide protection for viral nucleic acid and means of virus attachment to hosts' cells.
Viruses in extracellular state have virions have capsids which are protein coats that provide protection for viral nucleic acid and means of virus attachment to hosts' cells.
Which of the following are not self replicating? Viruses Viroids Prions Bacteria
Viruses, Viroids, and Prions Viruses, Viroids, and Prions are NOT self replicating. Bacteria is self replicating.
Give an example of a generalist virus?
West Nile Virus, can infect humans, birds, reptiles, etc.
Lysogenic conversion results when...?
When phages carry genes that alter phenotype of a bacterium, making it pathogenic
Most DNA animal viruses (blank) in the nucleus.
assemble
Replication of animal viruses has the same basic replication pathway as (blank)
bacteriophages
Most RNA animal viruses develop solely in the (blank).
cytoplasm
Naked animal viruses are released by exocytosis or (blank).
lysis Naked animal viruses are released by exocytosis or lysis.
Postive sense viral RNA can act as (tRNA or mRNA).
mRNA. + RNA can act as mRNA.
Most DNA animal viruses assemble in the (blank).
nucleus
Enveloped animal viruses may cause (blank) infections.
persistant Enveloped animal viruses may cause persistent infections.
Latent animal viruses are called ___________?
proviruses