Virology and Virus Structure
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Questions and Answers

What are viruses primarily classified based on?

  • Their geographical origin
  • Their reproduction methods
  • The diseases they cause
  • Their host cell type (correct)

What is a common method used to study the structure of viruses?

  • Ultrasound imaging
  • Light microscopy
  • NMR spectroscopy (correct)
  • Infrared spectroscopy

Which classification does not apply when categorizing viruses?

  • Type of nucleic acid
  • Host organism physiology (correct)
  • Geometrical shape of their capsid
  • Size of the virus

What are the two main types of nucleic acids viruses can have?

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

Which virus type is classified as a reverse-transcribing virus?

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

What is the size range of most viruses?

<p>30 nm to 450 nm (D)</p> Signup and view all the answers

How many viruses were listed in the latest report by the International Committee on Taxonomy of Viruses?

<p>5450 (D)</p> Signup and view all the answers

Which classification of RNA viruses is the least common?

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

What are viroids?

<p>Self-replicating RNA molecules that are circular and lack a capsid. (C)</p> Signup and view all the answers

Which of the following is considered a prion?

<p>A protein that induces other prions to change conformation. (B)</p> Signup and view all the answers

Which hypothesis suggests that viruses arose from non-living matter?

<p>Self-replicating RNA hypothesis. (B)</p> Signup and view all the answers

What distinguishes viruses from living organisms?

<p>Dependence on host cells for reproduction. (B)</p> Signup and view all the answers

What are oncoviruses known to contribute to?

<p>The development of certain types of cancers. (A)</p> Signup and view all the answers

Which disease is NOT caused by a virus?

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

Which of the following best describes satellite viruses?

<p>Viruses that can replicate only with the help of another virus. (B)</p> Signup and view all the answers

Where do viruses typically evolve?

<p>In concert with the evolution of their host organisms. (A)</p> Signup and view all the answers

Which of the following is a major cause of cervical cancer?

<p>Human papilloma virus (A)</p> Signup and view all the answers

What is the term used to describe the study of how viruses cause disease?

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

What do vaccinations primarily stimulate in order to protect against viral diseases?

<p>Antibody production (D)</p> Signup and view all the answers

What is the role of T cells in the immune response to viruses?

<p>They destroy host cells displaying viral fragments. (B)</p> Signup and view all the answers

What is the term for the measure of how effectively a virus causes disease?

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

What mechanism found in eukaryotes likely evolved as a defense against viruses?

<p>RNA interference (C)</p> Signup and view all the answers

Which of the following diseases is NOT associated with prions?

<p>Hepatitis C (C)</p> Signup and view all the answers

Why do lethal viral diseases present a paradox for the virus?

<p>Because most viruses are benign in their natural hosts. (C)</p> Signup and view all the answers

What is believed to cause lethal viral diseases to jump from one species to another?

<p>Accidental zoonotic transmission of benign viruses (C)</p> Signup and view all the answers

What was the first antiviral drug developed for treating viral diseases?

<p>Interferon (C)</p> Signup and view all the answers

Why are bacteriophages significant in the field of molecular biology?

<p>They can transduce genetic material between bacteria (C)</p> Signup and view all the answers

Which method is commonly used today for growing animal viruses?

<p>Human cell lines (D)</p> Signup and view all the answers

What is a major challenge faced in viral gene therapy?

<p>Rejection of the vector by the immune system (B)</p> Signup and view all the answers

What are oncolytic viruses primarily used for?

<p>Preferentially infecting cancer cells (C)</p> Signup and view all the answers

What role do modified retroviruses play in gene therapy?

<p>Transporting genes into host cell chromosomes (B)</p> Signup and view all the answers

Which of the following statements about phage therapy is correct?

<p>It is seeing renewed interest for combating bacterial diseases (B)</p> Signup and view all the answers

Flashcards

What are subviral particles?

Subviral particles are infectious agents smaller and simpler than viruses. They include viroids, satellites, and prions.

What are viroids?

Viroids are naked circular RNA molecules that infect plants. They lack a protein coat and replicate independently.

What are satellites?

Satellites are nucleic acid molecules that require a helper virus for infection and reproduction. They may or may not have a capsid.

What are prions?

Prions are infectious proteins that can exist in a pathological conformation, causing other prion molecules to fold the same way. This misfolding can lead to serious diseases.

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How did viruses arise?

The evolutionary relationships of viruses are complex and not always clear. Three hypotheses explain their origin: 1) From non-living matter, 2) From genome reduction of cellular life forms, and 3) From mobile genetic elements of cells.

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How does viral evolution occur?

Viral evolution often occurs in concert with the evolution of their hosts. This means that viruses and their hosts evolve together in a dynamic relationship.

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What are the characteristics of viruses?

Viruses are obligate intracellular parasites, meaning they must infect a host cell to reproduce. They don't engage in metabolism or movement on their own.

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What diseases do viruses cause?

Viruses cause a wide range of diseases, including common colds, flu, rabies, measles, and more serious conditions like hepatitis and AIDS.

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Viral Pathogenesis

The study of how viruses cause disease in their hosts.

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Virulence

The ability of a virus to cause disease, indicating how severe the disease it causes is.

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Antibodies

Proteins produced by the immune system that bind to and neutralize viruses.

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ELISA

A test that detects the presence of antibodies in blood serum, indicating past exposure to a virus.

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Cell-Mediated Immunity

A type of immunity involving T cells that recognise and destroy infected cells.

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RNA Interference

A cellular mechanism that uses enzymes to detect and destroy double-stranded RNA, a mechanism likely evolved to fight off viruses.

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Lethal Viral Disease Paradox

A paradox where a virus, by killing its host, destroys its own opportunity to spread.

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Benign Virus in Natural Host

A virus that causes disease in another species but may be beneficial to its natural host.

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Transduction

The transfer of genetic material from one bacterium to another by a virus.

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Bacteriophages

Viruses that infect bacteria and can be used as research tools in molecular biology.

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Phage Therapy

The use of bacteriophages to treat bacterial infections.

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Oncolytic Viruses

Viruses that preferentially infect cancer cells.

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Transfection

A process where a virus introduces new genes into a host cell.

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Viral gene therapy

Using viruses as carriers to deliver genes into cells, with potential applications for treating genetic diseases.

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Retrovirus

A type of virus that integrates its genetic material into the host's chromosome.

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Zoonosis

The natural host of a virus where it is typically benign but can cause serious disease in a new host species.

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What is Virology?

The study of viruses: their structure, classification, how they infect and reproduce in host cells, interactions with the host's immune system, the diseases they cause, isolation methods, and their applications in research and therapy.

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What is Viral Classification by Host?

A branch of virology that classifies viruses based on their host cell, such as animal viruses, plant viruses, fungal viruses, and bacteriophages.

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What is Viral Classification by Structure?

A method of classifying viruses based on the geometric shape of their capsid (often a helix or an icosahedron) or the presence or absence of an envelope surrounding the capsid.

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What is Viral Classification by Nucleic Acid and Replication?

A system for classifying viruses based on the type of nucleic acid they use as genetic material (DNA or RNA) and their replication strategy.

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What are DNA viruses?

Viruses that use DNA as their genetic material. They're further divided into double-stranded DNA viruses and single-stranded DNA viruses.

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What are RNA viruses?

Viruses that use RNA as their genetic material. They're classified into three categories: positive-sense single-stranded RNA viruses, negative-sense single-stranded RNA viruses, and double-stranded RNA viruses.

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What are Reverse Transcribing Viruses?

Viruses that use reverse transcription to copy their RNA genome into DNA, which then integrates into the host's genome. They're classified as double-stranded reverse-transcribing DNA viruses and single-stranded reverse-transcribing RNA viruses.

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How many viruses have been identified?

The latest report by the International Committee on Taxonomy of Viruses (2005) lists over 5,450 viruses categorized into species, genera, families, and orders.

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Study Notes

Virology

  • Virology is the study of viruses, submicroscopic parasitic particles with genetic material in a protein coat.
  • It examines viral structure, classification, evolution, infection methods, host cell exploitation for reproduction, interactions with host physiology and immunity, diseases caused, isolation and culture techniques, and applications in research and therapy.
  • It's a subfield of microbiology or medicine.

Virus Structure and Classification

  • Virus classification is a major branch of virology.
  • Viruses are classified by the host cell they infect (animal, plant, fungal, bacteriophages).
  • Viruses can have different shapes, including helices and icosahedrons, and may or may not have a lipid envelope.
  • Sizes range from 30 nm to 450 nm, making them invisible with light microscopes.
  • Electron microscopy, NMR, and X-ray crystallography are used to study their structure.
  • Viruses are further classified based on the type of nucleic acid (DNA or RNA) and their replication method.

Viral Diseases and Host Defenses

  • Viral diseases cause significant health problems (common cold, influenza, rabies, measles, diarrhea, hepatitis, dengue, yellow fever, polio, smallpox, AIDS, herpes simplex.
  • Some viruses contribute to cancer development, such as HPV and cervical cancer, and hepatitis B and C linked to liver cancer.
  • Viruses are not alive and do not have metabolism, move on their own or have independent reproduction.
  • They need host cells to reproduce and the question of whether they are alive or not is defined by their features.

Molecular Biology Research and Viral Therapy

  • Bacteriophages (viruses that infect bacteria) are useful as research tools.
  • They are used for horizontal gene transfer, understanding genetic code, ribosome function, constructing recombinant DNA and genetic libraries.
  • Viral genes and promoters are currently employed in molecular biology research.
  • Phage Therapy utilizes bacteriophages to combat bacterial infections.
  • Oncolytic viruses preferentially target and infect cancer cells. Efforts are ongoing for potential use in viral therapy methods to combat cancer.

Other applications of Viruses

  • Viruses are being employed in gene therapy for genetic diseases and in nanotechnology for various applications.
  • Modified retroviruses are used to transfer genes into host cells.
  • Viruses are applied to introduce new genes in hosts for transformation or transfection for gene therapy, but the immune system rejection of viruses often is a major problem during the process.

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Description

Explore the fascinating world of virology with this quiz focusing on virus structure and classification. Understand the intricate details of viral shapes, sizes, and their classification based on host types and nucleic acid. This quiz will test your knowledge on the fundamental concepts and techniques used in virology.

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