Viral Classification, Structure, and Replication
38 Questions
4 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which characteristic primarily defines viruses?

  • Possession of a complex cellular structure with organelles.
  • Ability to reproduce independently in any environment.
  • Large size, allowing easy observation under a standard microscope.
  • Obligate intracellular parasitic behavior. (correct)

What is the historical significance of describing viruses as 'filterable agents'?

  • It describes their complex method of movement through the air.
  • It highlights their unique genetic material compared to bacteria.
  • It refers to their ability to be easily cultured in laboratory settings.
  • It indicates their small size, enabling them to pass through filters that trap bacteria. (correct)

A new virus is discovered that can integrate its genetic material into a host cell but cannot complete its replication cycle without a helper virus. How would this virus be classified based on the information provided?

  • Defective Virus (correct)
  • Lytic Virus
  • Temperate Virus
  • Autonomous Virus

If a virus loses its ability to synthesize proteins, what essential characteristic would it be lacking?

<p>The capacity to produce structural components and enzymes needed for replication. (A)</p> Signup and view all the answers

A researcher is studying a newly discovered virus. Initial tests show the virus can infect a cell, but no new viral particles are produced. Which step of the viral replication cycle is most likely being blocked?

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

Which of the following characteristics distinguishes viral reproduction from bacterial binary fission?

<p>Viruses reproduce through the assembly of individual components. (B)</p> Signup and view all the answers

A newly discovered virus is found to have a high mutation rate. Which of the following factors would most likely contribute to this?

<p>An RNA genome that lacks proofreading mechanisms. (B)</p> Signup and view all the answers

A researcher identifies a novel virus that infects the enteric system. Based on viral classification, which characteristic is being used?

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

A virus is classified as an arbovirus. What does this classification indicate about the virus?

<p>It is transmitted by arthropod vectors. (B)</p> Signup and view all the answers

Which of the following is the most consistent and current means of classifying viruses?

<p>The physiological and biochemical characteristics. (B)</p> Signup and view all the answers

Which of the following characteristics can be used to classify viruses?

<p>Size, presence or absence of an envelope, and type of genome. (B)</p> Signup and view all the answers

A patient is diagnosed with an infection caused by a virus in the Herpesviridae family. Which of the following viruses could be responsible?

<p>Epstein-Barr virus (B)</p> Signup and view all the answers

A new antiviral drug is designed to target a specific virus from the Retroviridae family. Which virus is most likely to be the target?

<p>Human immunodeficiency virus (C)</p> Signup and view all the answers

Which of the following viruses is associated with the Orthomyxoviridae family?

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

A patient presents with symptoms consistent with viral hemorrhagic fever. Which of the following viral families should be considered in the differential diagnosis?

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

A virus measures 250 nm in diameter and contains a complex genome. Which of the following characteristics is MOST likely?

<p>It can encode a larger number of proteins compared to smaller viruses. (C)</p> Signup and view all the answers

A patient is diagnosed with an infection caused by a virus that lacks a lipid envelope. Which characteristic is LEAST likely to be associated with this virus?

<p>Direct entry into the host cell via fusion with the cell membrane. (C)</p> Signup and view all the answers

During viral replication, a specific enzyme is required to convert the viral RNA genome into DNA within the host cell. Which virus is MOST likely to require that enzyme?

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

A public health official is investigating an outbreak of gastroenteritis traced to contaminated shellfish. Which viral family is the MOST likely causative agent?

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

A patient presents with symptoms of fever, headache, and rash after being bitten by a mosquito. Which virus should be considered as a possible cause?

<p>West Nile virus (D)</p> Signup and view all the answers

A researcher is studying a virus that selectively targets and infects red blood cell precursors. Which virus is MOST likely the subject of their research?

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

A new antiviral drug is designed to inhibit a viral enzyme essential for cleaving a large polypeptide into functional proteins. Which virus would be LEAST affected by this drug?

<p>A virus that directly translates its genome into functional proteins. (B)</p> Signup and view all the answers

An emerging viral disease is characterized by its ability to establish a persistent infection in the host and integrate its genetic material into the host cell's chromosomes. Which virus exhibits this?

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

Which of the following characteristics is associated with capsid viruses, enabling their transmission through harsh environments?

<p>Resistance to drying and detergents (C)</p> Signup and view all the answers

If a virus relies on a positive-sense RNA genome, what immediate advantage does this provide to the virus upon entering a host cell?

<p>The genome can be immediately translated into proteins. (B)</p> Signup and view all the answers

What is the primary role of viral attachment proteins (VAPs) located on the surface of a virus?

<p>To facilitate the virus's entry into the host cell (A)</p> Signup and view all the answers

Which structural feature of enveloped viruses makes them susceptible to inactivation by drying and solvents?

<p>The membranous structure derived from host cell membranes (A)</p> Signup and view all the answers

How would antibodies generated against the surface structures of a virus act to prevent infection?

<p>By blocking the virus's ability to attach to host cells (B)</p> Signup and view all the answers

In the context of viral capsid assembly, what is the role of 'protomers' and 'capsomeres'?

<p>They are individual protein subunits that assemble into larger capsid units. (A)</p> Signup and view all the answers

How does segmentation of a viral RNA genome contribute to viral evolution and diversity?

<p>It facilitates genetic reassortment, leading to new viral strains. (C)</p> Signup and view all the answers

What distinguishes helical viruses from icosahedral viruses in terms of their structure?

<p>Helical viruses appear rod-shaped, while icosahedral viruses have a symmetrical, multifaceted structure. (B)</p> Signup and view all the answers

If a virus is classified as non-symmetric, what does this indicate about its structure compared to symmetric viruses?

<p>It has a complex structure not based on helical or icosahedral symmetry. (B)</p> Signup and view all the answers

How does the presence of a viral envelope influence a virus's ability to survive outside a host, compared to a non-enveloped virus?

<p>Enveloped viruses are generally more susceptible to environmental stressors. (C)</p> Signup and view all the answers

What is the role of reverse transcriptase in the context of viral replication?

<p>It is used to make DNA from an RNA template. (D)</p> Signup and view all the answers

Considering the Baltimore classification system, what does it mean if a virus has a '+ RNA' genome?

<p>The viral genome can be directly translated into proteins. (C)</p> Signup and view all the answers

How mutations impact the effectiveness of vaccines targeting surface spike proteins?

<p>Mutations can alter spike protein structure, potentially reducing vaccine effectiveness. (D)</p> Signup and view all the answers

What is the role of RDRP (RNA-dependent RNA polymerase) in viral replication, specifically for viruses with RNA genomes?

<p>To synthesize RNA from an RNA template. (B)</p> Signup and view all the answers

In enveloped viruses, where do the lipids, proteins, and glycoproteins composing the envelope originate?

<p>They are derived from the host cell membranes. (A)</p> Signup and view all the answers

Flashcards

Obligate intracellular parasites

Viruses that can only replicate inside a living host cell.

Filterable agents

Early term used to describe viruses due to their small size that could pass through filters.

Virus replication

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

Size of viruses

Viruses are generally much smaller than bacteria, making them unique.

Signup and view all the flashcards

Viral structure

Viruses consist of genetic material surrounded by a protein coat.

Signup and view all the flashcards

Virus

A microorganism that depends on a host for replication and cannot reproduce independently.

Signup and view all the flashcards

Viral Assembly

The process by which viruses put together their components to form new virus particles instead of dividing like cells.

Signup and view all the flashcards

Naked Virus

A type of virus that lacks an envelope and consists only of nucleic acid and protein.

Signup and view all the flashcards

Classification of Viruses

The system used to categorize viruses based on characteristics such as disease association, tissue targeting, or replication method.

Signup and view all the flashcards

DNA Virus Families

Groups of viruses with DNA genomes, divided into families like Poxviridae and Herpesviridae.

Signup and view all the flashcards

RNA Virus Families

Groups of viruses with RNA genomes, including families like Paramyxoviridae and Retroviridae.

Signup and view all the flashcards

Poxviridae

A family of DNA viruses that includes smallpox and other related viruses.

Signup and view all the flashcards

Orthomyxoviridae

A family of RNA viruses that includes Influenza A, B, and C viruses.

Signup and view all the flashcards

Arenaviridae

A family of RNA viruses that includes Lassa fever virus and related viruses.

Signup and view all the flashcards

Retroviridae

A family of RNA viruses that includes the human immunodeficiency virus (HIV).

Signup and view all the flashcards

Nucleic acid genome

The genetic material of a virus, which can be RNA or DNA.

Signup and view all the flashcards

Capsid

A protein coat that encases the viral genome and protects it.

Signup and view all the flashcards

Envelope

A lipid bilayer surrounding the nucleocapsid in some viruses.

Signup and view all the flashcards

Virion

A complete virus particle that consists of nucleic acid, capsid, and sometimes an envelope.

Signup and view all the flashcards

Virion size measurement

Measured in nanometers (nm), with most clinically important viruses ranging from 18 to 300 nm.

Signup and view all the flashcards

Larger virions

Can hold a larger genome and are more complex, encoding more proteins.

Signup and view all the flashcards

Parvoviruses

Viruses that are around 18 nm in size, smaller viruses.

Signup and view all the flashcards

Delta agent

A special type of virus associated with hepatitis, acting as a co-infecting entity.

Signup and view all the flashcards

Viral genome

The genetic material of a virus, can be DNA or RNA.

Signup and view all the flashcards

Single stranded DNA

A type of DNA that consists of a single strand.

Signup and view all the flashcards

Positive sense RNA

RNA that can be directly translated into proteins.

Signup and view all the flashcards

Negative sense RNA

RNA that is complementary to mRNA and must be transcribed first.

Signup and view all the flashcards

Viral attachment protein (VAP)

Structure that helps a virus attach to host cells.

Signup and view all the flashcards

Viral envelope

A lipid membrane surrounding some viruses, derived from host cell membranes.

Signup and view all the flashcards

Capsomeres

The individual protein units that make up a capsid.

Signup and view all the flashcards

Icosadeltahedron

A symmetrical viral shape composed of 20 triangular faces.

Signup and view all the flashcards

Helical symmetry

A viral structure that appears rod-like, twisted in shape.

Signup and view all the flashcards

Nonsymmetric viruses

Viruses with complex structures, often seen in bacteriophages.

Signup and view all the flashcards

Enveloped viruses

Viruses that have an outer lipid membrane which is fragile.

Signup and view all the flashcards

Recombinant viruses

Viruses formed by combining genetic material from different viral strains.

Signup and view all the flashcards

Reverse transcriptase

An enzyme that converts RNA into DNA in some viruses.

Signup and view all the flashcards

Viral transmission routes

Methods by which viruses spread, including droplets, blood, and fecal-oral routes.

Signup and view all the flashcards

Study Notes

Viral Classification, Structure, and Replication

  • Viruses are filterable agents, obligate intracellular parasites, requiring host machinery for replication. They reproduce by assembling individual components rather than binary fission.
  • Viruses consist of nucleic acid (DNA or RNA), protein, and sometimes a membrane (envelope).
  • Viral structure and genetics have evolved to maximize infection of specific hosts.

Viral Classification

  • Viral names can describe characteristics or the disease they cause, or tissue/geographic location of first identification.
  • Viruses are classified by various characteristics, such as disease, target tissue, transmission method, and morphology (size, presence of envelope, type of genome).
  • Current classification relies on biochemical and physiological traits. DNA viruses are grouped into ~7 families, and RNA viruses categorized into at least 13 families.

Virion Structure

  • Virions (virus particles) consist of a nucleic acid genome (DNA or RNA), a capsid (protein coat), and sometimes an envelope (lipid membrane).
  • Genomes can be single- or double-stranded DNA or RNA, linear or circular, and some RNA genomes are positive-sense (like mRNA) or negative-sense (complement to mRNA), some segmented.
  • Baltimore classification groups viruses based on their genetic material and replication strategies
  • Virion structures include symmetric (helical and icosahedral) and asymmetric (complex) shapes.

Virion Structure - Additional Details

  • Capsid: The protein coat surrounding the viral genome, providing protection and structural support. Composed of subunits (protomers), which assemble into larger structures (capsomers) that make up the procapsid and finally the mature capsid.
  • Envelope: A lipid membrane surrounding the capsid of certain viruses; derived from the host cell membrane; containing viral glycoproteins involved in host cell attachment (e.g., HIV's gp120).
  • Viral Morphology: Viruses can be helical, icosahedral, or complex.

Viral Structure - Transmission

  • Viral surface structures (capsids or envelopes) are crucial for interaction with host cells and enable transmission.
  • VAP (viral attachment protein) facilitates virus entry; disruption of these structures inactivates the virus
  • Some viruses are resistant to harsh environments (e.g., drying, acid, detergents) and can be transmitted in wide range of conditions, like sewage, while others require aqueous solutions for survival

Viral Structure - Families and Target Cells

  • Various virus families have distinct characteristics and associated target cells (e.g., epithelial cells, nerve cells, blood precursors).
  • Specific viral attachment proteins (VAPs) and receptors on target cells are crucial for viral entry. HIV uses CD4 and CCR5 receptors, while influenza has HA and NA proteins involved in transmission.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Viral Classification, Structure, and Replication - Chapter 44 PDF

Description

Explore viral structure, genetics, and classification based on disease, target tissue, and morphology. Discover how viruses, as obligate intracellular parasites, replicate by assembling individual components using host machinery. Understand the biochemical and physiological traits used to classify viruses.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser