Virology Quiz: Virus Entry and Replication
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Questions and Answers

What is the primary mechanism by which non-enveloped viruses enter a host cell?

  • Active transport across the cell membrane
  • Direct fusion with the plasma membrane
  • Receptor attachment and release of viral nucleic acids
  • Endocytosis, forming a vesicle (correct)

Which process involves the breakdown of the viral capsid to release nucleic acids?

  • Uncoating (correct)
  • Budding
  • Endocytosis
  • Fusion

What is the initial step for enveloped viruses to enter a host cell?

  • Receptor-mediated transfer to the cytoplasm
  • Direct penetration
  • Endocytosis
  • Fusion of the viral envelope with the plasma membrane (correct)

What are the two key stages that occur after the virus uncoats?

<p>Replication of nucleic acids and capsid protein (C)</p> Signup and view all the answers

What is the typical size range for most phages?

<p>24 - 200 nm (D)</p> Signup and view all the answers

During viral replication, what term describes the assembled viral proteins and newly replicated nucleic acids?

<p>Nucleocapsid (A)</p> Signup and view all the answers

What is the primary effect of a hypovirus infection on a fungus?

<p>It causes the fungus to become hypovirulent. (D)</p> Signup and view all the answers

Based on their nucleic acid type, which of these is NOT a primary classification of viruses?

<p>Double-stranded protein viruses (B)</p> Signup and view all the answers

Which of the following is an example of a double stranded DNA virus?

<p>Herpes virus type 1 (D)</p> Signup and view all the answers

What is the size range for most bacteriophages?

<p>10-200 nm (C)</p> Signup and view all the answers

How does the hypovirus spread from tree to tree according to the text?

<p>Through mites carrying the virus in their droppings. (A)</p> Signup and view all the answers

What is the role of the host's RNA polymerase during the replication of a double-stranded DNA virus?

<p>To transcribe mRNA from the viral DNA. (B)</p> Signup and view all the answers

What is the name of the process by which viruses exit the host cell ?

<p>Budding (B)</p> Signup and view all the answers

Which of the following is the scientific name of the fungus that is mentioned as a host in the text?

<p>Cryphonectria parasitica (B)</p> Signup and view all the answers

Which of the following is a known disease caused by Adenoviruses?

<p>The common cold. (D)</p> Signup and view all the answers

What is a key function of the viral proteins produced during the replication of double-stranded DNA viruses?

<p>They form part of the new viral capsids. (B)</p> Signup and view all the answers

According to the text what type of nucleic acid does the Rubella virus have?

<p>Positive sense ssRNA (C)</p> Signup and view all the answers

What is a major difference between positive-sense and negative-sense single-stranded RNA viruses?

<p>Positive-sense RNA can be directly translated, while negative-sense RNA needs to be transcribed first. (B)</p> Signup and view all the answers

What is a key difference between positive-sense and negative-sense ssRNA viruses?

<p>Positive-sense genomes can be directly translated into viral proteins, while negative-sense cannot. (A)</p> Signup and view all the answers

Which of the following are retroviruses?

<p>Human Immunodeficiency Virus. (B)</p> Signup and view all the answers

If a virus is classified as a single-stranded DNA virus, what is a characteristic about the genome structure?

<p>It has one strand of DNA. (C)</p> Signup and view all the answers

Which of the following best describes the term 'obligate intracellular parasite' as it relates to viruses?

<p>Viruses require a host cell for replication and cannot reproduce outside a host. (B)</p> Signup and view all the answers

Which of the following is NOT a possible type of viral genome?

<p>A combination of both DNA and RNA. (A)</p> Signup and view all the answers

What is the primary source of a viral envelope?

<p>The envelope is acquired from a hijacked portion of the host cell membrane. (B)</p> Signup and view all the answers

How do viruses, which are non-motile, initially come into contact with a host cell?

<p>Viruses are transported passively through means such as aerosols or blood flow. (A)</p> Signup and view all the answers

What is the function of the receptor that is produced by the host cell in enveloped viruses?

<p>To bind with the virus and help it enter the host cell. (A)</p> Signup and view all the answers

What key structural components are absent in viruses, unlike prokaryotic and eukaryotic cells?

<p>Cytoplasm, organelles, and a nucleus. (B)</p> Signup and view all the answers

Which type of virus, classified by its nucleic acid, can cause gastro-enteritis in chickens?

<p>ssDNA viruses. (B)</p> Signup and view all the answers

How do non-enveloped viruses attach to a host?

<p>Using a protein on the viral capsid as a receptor. (B)</p> Signup and view all the answers

Which of the following is NOT a typical route of transmission for adenoviruses in humans?

<p>Ingesting contaminated food items. (A)</p> Signup and view all the answers

What is the primary nucleic acid type associated with Aveparvovirus?

<p>Single-stranded DNA (B)</p> Signup and view all the answers

Which of the following symptoms is NOT associated with Aveparvovirus infection in chickens?

<p>Increased egg hatching rate (C)</p> Signup and view all the answers

A study found that 27% of healthy birds tested positive for Parvovirus. What does this finding most likely indicate?

<p>Birds can be carriers of the virus without showing symptoms. (D)</p> Signup and view all the answers

What type of virus is Hypoviridae?

<p>Double-stranded RNA virus (A)</p> Signup and view all the answers

How does a double stranded RNA virus replicate its genome?

<p>By using a viral RNA polymerase to transcribe viral mRNA. (B)</p> Signup and view all the answers

What is the unusual feature regarding Hypovirus infections?

<p>They infect a type of fungus that parasitizes trees. (D)</p> Signup and view all the answers

Which of these best describes the effect of Hypovirus on its host?

<p>Decreased virulence. (C)</p> Signup and view all the answers

Which characteristic is unique to negative-sense single-stranded RNA viruses?

<p>They require viral RNA polymerase to produce a positive-sense strand. (C)</p> Signup and view all the answers

What is the role of viral RNA polymerase in the replication of negative-sense single-stranded RNA viruses?

<p>To produce a positive-sense RNA strand from the negative-sense viral RNA. (A)</p> Signup and view all the answers

How does the genetic material of a retrovirus become permanently integrated into host cell's genome?

<p>Through reverse transcriptase, RNA is transcribed into DNA, which is then incorporated into the host cell's DNA. (C)</p> Signup and view all the answers

What is the typical first sign of Rubella in children who show symptoms?

<p>A red rash on the face spreading to the body (C)</p> Signup and view all the answers

Which enzyme is characteristic of retroviruses and enables them to integrate their genetic material into the host's genome?

<p>Reverse transcriptase (D)</p> Signup and view all the answers

What do both negative-sense single-stranded RNA viruses and retroviruses have in common?

<p>They both require an enzyme to convert their RNA to another form of nucleic acid at some stage of their life cycle. (D)</p> Signup and view all the answers

How is rubella generally spread?

<p>Through aerosols droplets. (C)</p> Signup and view all the answers

What is a key feature of retroviruses that distinguishes them from other RNA viruses?

<p>They use reverse transcriptase to integrate into the host genome. (D)</p> Signup and view all the answers

Flashcards

dsDNA viruses

Viruses that contain double-stranded DNA as their genetic material.

ssDNA viruses

Viruses that contain single-stranded DNA as their genetic material.

Adenovirus

A type of virus that infects humans and can cause a variety of illnesses, including the common cold, sore throat, and pneumonia.

Viral replication

The process by which a virus replicates inside a host cell.

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Viral enzymes

Enzymes produced by viruses that help the virus replicate.

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Viral capsid

The protein coat that surrounds a virus's genetic material.

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Virology

The study of viruses.

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Virus classification

A collection of viruses that are grouped based on their genetic material.

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Viral Penetration

The process by which a virus enters a host cell.

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Non-Enveloped Virus

A virus that does not have a lipid envelope surrounding its capsid.

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Endocytosis

A process where a virus binds to a host cell's receptor and is engulfed into a vesicle.

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Enveloped Virus

A virus that has a lipid envelope surrounding its capsid.

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Fusion

The process where an enveloped virus fuses its membrane with the host cell membrane.

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Viral Uncoating

The breakdown of the viral capsid to release the nucleic acid into the host cell.

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Viral Exit

The release of new viral particles from the host cell.

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How are adenoviruses spread?

Adenoviruses can be spread through close personal contact, such as touching or shaking hands.

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How else can adenoviruses be spread?

Adenoviruses can spread through the air by coughing and sneezing.

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How can adenoviruses spread through objects?

Adenoviruses can spread through touching an object or surface contaminated with adenoviruses, then touching your mouth, nose, or eyes before washing your hands.

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What is Aveparvovirus?

Aveparvovirus is a type of virus that affects chickens and turkeys.

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What are the symptoms of Aveparvovirus in chickens?

Aveparvovirus infection can lead to impaired growth, poor feathering, diarrhea, distended intestines, and weakened bones in chickens.

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What other complications can Aveparvovirus cause?

Aveparvovirus infection can also lead to decreased hatching of eggs and cerebellar hyperplasia.

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What is Hypoviridae?

Hypoviridae is a family of viruses that infect fungi.

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What is the impact of Hypovirus on fungi?

Hypovirus infection of fungi can lead to decreased virulence of the fungus, potentially impacting its ability to infect trees.

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Hypovirus

A virus that infects a fungal pathogen, making it less harmful to its host plant.

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Chestnut blight

A fungal disease that affects chestnut trees, caused by the fungus Cryphonectria parasitica.

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Cryphonectria hypovirus 1 (Hypovirus)

A virus that can infect the fungus Cryphonectria parasitica, reducing its virulence and allowing chestnut trees to recover from infection.

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Virulence

The ability of a pathogen to cause disease.

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Hypovirulent

A form of a pathogen that is less harmful than its normal form.

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What are viruses?

Viruses are very small infectious agents that rely on a host cell to replicate.

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Obligate intracellular parasites

It means that viruses cannot replicate on their own and require a living host cell to reproduce.

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Viral nucleic acid

Viral genomes carry either DNA or RNA but not both, which can be either single or double stranded.

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Viral envelope

Some viruses acquire an envelope made of phospholipids and glycoproteins from their host cell during replication.

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Viral attachment

The process by which a virus attaches to a host cell. It's the first step in the viral infection cycle.

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Enveloped virus attachment

Enveloped viruses utilize receptors on their host's surface to attach. These receptors are produced by the host cell itself.

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Non-enveloped virus attachment

Non-enveloped viruses utilize protein on their capsid to act as a receptor for attachment to the host cell.

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Viral transmission

Viruses are not capable of independent movement. They rely on passive transportation through various routes.

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Negative sense single-stranded RNA virus

A type of virus whose genome is single-stranded RNA and needs to be converted into a positive sense strand using a viral RNA polymerase before it can be used to produce proteins.

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Positive sense single-stranded RNA virus

A type of virus whose genome is single-stranded RNA and can immediately act as mRNA to produce proteins.

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Reverse Transcriptase (RT)

An enzyme found in some viruses that converts RNA into DNA, effectively reversing the usual flow of genetic information.

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Retroviruses

A group of viruses that use RNA as their genetic material and incorporate their DNA into the host cell's genome.

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Positive sense RNA replication

A type of viral replication where the virus's RNA genome acts as mRNA and is directly used by the host cell to produce viral proteins.

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Negative sense RNA replication

A type of viral replication where the virus's RNA genome must first be converted into a positive sense strand using a viral RNA polymerase before it can be translated into proteins.

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Viral RNA polymerase

A viral enzyme responsible for creating more copies of a virus's genome.

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Study Notes

Virus Structure and Function

  • Viruses are small, infectious agents.
  • Viruses are obligate intracellular parasites.
  • Viruses lack cytoplasm, organelles, and a nucleus.
  • Viruses differ structurally from prokaryotic and eukaryotic cells.
  • Viruses have a unique structure - either enveloped or non-enveloped.
  • Enveloped viruses have a lipid membrane acquired from the host cell.
  • Non-enveloped viruses lack a lipid membrane.

Viral Nucleic Acids

  • Viral genomes consist of either DNA or RNA, but not both.
  • Viruses can have double-stranded or single-stranded DNA or RNA.
  • Viral nucleic acids must be uncoated to begin replication.

Viral Classification

  • Viruses are classified by their nucleic acid (DNA or RNA) and whether they have an envelope.
  • Examples of virus types include dsDNA, ssDNA, dsRNA, ssRNA, positive sense ssRNA viruses and negative sense ssRNA viruses, retroviruses.

Viral Replication

  • Viral replication involves nucleic acid replication and capsid protein replication.
  • Viruses utilize host cell machinery for replication.
  • The viral proteins assemble into complete virus particles (virions) around the newly replicated nucleic acids.
  • These virions are now referred to as nucleocapsids.

Viral Attachment and Entry

  • Viruses attach to host cells through specific receptors.
  • Different viruses attach and penetrate in different ways.
  • Enveloped viruses enter host cells through membrane fusion.
  • Non-enveloped viruses enter through endocytosis.

Viral Exit

  • Viruses exist from host cells through budding.

Viral Infections

  • Viruses can cause significant disease in humans and animals. This can result in suffering, disease and decreased food supplies.
  • Viral outbreaks have received significant attention recently.
  • Viral infections can also affect plants causing similar issues to those encountered in humans and animals.

Examples of Viruses and Diseases Affecting Humans

  • Zika virus
  • Foot and Mouth Disease
  • Adenovirus (colds, sore throats, bronchitis, pneumonia, diarrhoea, conjunctivitis)
  • Rubella (a mild illness)
  • Retroviruses (bovine leukaemia virus, human immunodeficiency virus, simian immunodeficiency virus)
  • Hypovirus (infects fungi, can cause fungal diseases in trees)
  • Aveparvovirus (infects chickens; Runting-stunting syndrome)

Viral Replication Summary

  • The replication of viruses differs based on the viral type.
  • There are different pathways of viral replication depending on type of genome.
  • For enveloped viruses the replication pathway differs to that of non-enveloped viruses.

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Description

Test your knowledge on the mechanisms of virus entry, uncoating processes, and characteristics of different viruses. This quiz also covers the role of host organisms in viral replication and effects of viral infections. Perfect for students studying virology or microbiology.

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