Introduction to Viruses
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Questions and Answers

What is the primary reason viruses are considered obligate parasites?

  • They require a living cell for reproduction. (correct)
  • They can survive outside a host cell.
  • They possess their own replication machinery.
  • They can reproduce independently.

Which component of a virus is responsible for enclosing its nucleic acid core?

  • Capsid (correct)
  • Spikes
  • Genome
  • Envelope

What defines a retrovirus specifically?

  • It uses reverse transcriptase to transcribe RNA into DNA. (correct)
  • It can only infect plant cells.
  • It has a double-stranded DNA genome.
  • It lacks a lipid envelope.

Which of the following viruses is NOT mentioned as causing a viral disease in humans?

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

What is a common characteristic of viroids?

<p>They are composed of RNA only. (A)</p> Signup and view all the answers

How does a latent virus behave within a host cell?

<p>It becomes inactive but can be reactivated. (A)</p> Signup and view all the answers

Which viral disease is typically characterized by high fever and body aches?

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

What is a common size range for viruses compared to bacteria?

<p>0.03 to 0.2 micrometer (B)</p> Signup and view all the answers

What role do spikes play in the structure of a virus?

<p>They help in the attachment to host cells. (B)</p> Signup and view all the answers

Which of the following statements about the viral genome is true?

<p>It may consist of either DNA or RNA. (B)</p> Signup and view all the answers

What is the difference between antigenic drift and antigenic shift in viruses?

<p>Antigenic drift involves small changes in the virus, while antigenic shift involves new combinations of surface spikes. (A)</p> Signup and view all the answers

Which of the following statements about measles is true?

<p>The MMR vaccine protects against measles, mumps, and rubella. (D)</p> Signup and view all the answers

What is a key characteristic of herpesviruses?

<p>They remain latent much of the time. (D)</p> Signup and view all the answers

What challenge do antiviral drugs face when targeting viral replication?

<p>Developing drugs that affect viral replication without harming host cells is difficult. (A)</p> Signup and view all the answers

What are viroids primarily known for?

<p>Infecting only plant cells and causing disease. (A)</p> Signup and view all the answers

Which of the following describes prions?

<p>They cause degenerative diseases in the nervous system by altering protein shapes. (C)</p> Signup and view all the answers

How are prions typically transmitted?

<p>By ingestion of infected tissues. (C)</p> Signup and view all the answers

Which disease is caused by the varicella-zoster virus?

<p>Chickenpox and shingles. (C)</p> Signup and view all the answers

What factual error is common regarding the use of antibiotics?

<p>Antibiotics can treat viral infections. (B)</p> Signup and view all the answers

Which virus is associated with infectious mononucleosis?

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

What is the main characteristic that distinguishes retroviruses from other viruses?

<p>They contain RNA as their genetic material (A)</p> Signup and view all the answers

What function do the spikes on a virus serve?

<p>They assist in attaching the virus to potential host cells (C)</p> Signup and view all the answers

Which type of virus can integrate its cDNA into the host's genome?

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

Which of the following statements about latency in viruses is true?

<p>Latency helps the virus avoid detection by the host immune system (C)</p> Signup and view all the answers

How do viroids primarily reproduce?

<p>By utilizing host cell RNA polymerase (D)</p> Signup and view all the answers

What type of nucleic acid can be found in viruses?

<p>Either DNA or RNA (C)</p> Signup and view all the answers

Which of the following viral diseases is characterized by mild symptoms and typically resolves within a week?

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

What is a common feature of prions?

<p>They consist only of proteins (C)</p> Signup and view all the answers

Which of the following viruses specifically infects bacteria?

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

Which viral structure is responsible for protecting the viral genome?

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

What can antigenic shift potentially lead to in viral diseases?

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

What is one of the main reasons antiviral drugs are difficult to develop?

<p>Viruses replicate within host cells (B)</p> Signup and view all the answers

Which disease is associated with the Epstein–Barr virus?

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

What is a key consequence of a normal protein changing into a prion?

<p>Degenerative diseases in the nervous system (C)</p> Signup and view all the answers

Which virus primarily causes genital herpes?

<p>Herpes simplex type 2 (A)</p> Signup and view all the answers

What is the incubation period for measles before symptoms appear?

<p>7 to 12 days (C)</p> Signup and view all the answers

How are prions primarily transmitted?

<p>Ingestion of infected tissues (A)</p> Signup and view all the answers

What is the fatality rate of measles in less-developed countries?

<p>10% to 15% (B)</p> Signup and view all the answers

Which statement about antibiotic use against viruses is correct?

<p>Antibiotics do not affect viruses. (B)</p> Signup and view all the answers

What is the primary function of the capsid in a virus?

<p>To protect the viral genome (A)</p> Signup and view all the answers

What distinguishes the reproductive cycle of retroviruses from other viruses?

<p>They utilize reverse transcriptase to convert RNA into DNA (C)</p> Signup and view all the answers

Which of the following viruses is known to have a significant period of latency?

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

What is a characteristic of viroids?

<p>They are RNA molecules that can replicate independently (A)</p> Signup and view all the answers

Which type of viral genome can be double-stranded?

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

How does a viral infection typically progress within a host cell?

<p>Latency followed by replication upon stress (C)</p> Signup and view all the answers

What is a common feature of both the common cold and influenza?

<p>Both are caused by RNA viruses (C)</p> Signup and view all the answers

What is the role of reverse transcriptase in retroviruses?

<p>To convert RNA into DNA for integration into the host genome (B)</p> Signup and view all the answers

What is the significance of antigenic drift in viruses?

<p>It refers to minor changes in the virus that may affect immunity. (A)</p> Signup and view all the answers

What is the primary mode of transmission for measles?

<p>Respiratory route. (A)</p> Signup and view all the answers

Why are antiviral drugs difficult to develop?

<p>Targeting viruses often harms host cells. (D)</p> Signup and view all the answers

What type of pathogens are viroids and prions categorized as?

<p>Acellular pathogens. (C)</p> Signup and view all the answers

Which of the following diseases is associated with prions?

<p>Chronic wasting disease. (D)</p> Signup and view all the answers

What characterizes the replication process of viroids?

<p>They replicate independently within host cell nuclei. (A)</p> Signup and view all the answers

Which herpesvirus is commonly associated with cold sores?

<p>Herpes simplex type 1. (C)</p> Signup and view all the answers

What is one potential outcome of antigenic shift in viruses?

<p>Creation of new viral strains that can cause pandemics. (C)</p> Signup and view all the answers

What is the incubation period for measles symptoms to appear?

<p>7 to 12 days. (A)</p> Signup and view all the answers

Which statement about antibiotics is correct?

<p>Antibiotics are effective only against bacteria. (A)</p> Signup and view all the answers

Flashcards

Virus

Acellular structure needing a living cell to reproduce.

Obligate parasite

Organism that requires a host organism to live and reproduce; viruses are obligate parasites.

Viral reproduction

Uses host cell's machinery to replicate.

Viral size

Much smaller than bacteria (0.03 to 0.2 micrometer).

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Viral structure

Variety of shapes (helix, sphere, polyhedron, etc.).

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Viral components

Capsid (protein coat) and nucleic acid core (DNA or RNA).

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Retrovirus

Virus with RNA genome and reverse transcriptase.

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Reverse transcriptase

Enzyme that converts RNA to DNA in retroviruses.

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Latency (virus)

Dormant state of a virus within a host cell.

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Viral Diseases

Can cause common cold, flu, and other maladies.

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Antigenic Drift

Small changes in a virus's antigens (surface proteins).

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Antigenic Shift

Major changes in a virus's antigens causing new combinations of surface spikes.

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Measles

A highly contagious human disease spread through respiratory routes.

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Incubation Period (Measles)

The time between measles infection and the appearance of symptoms.

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Herpesviruses

Viruses that can remain dormant (latent) in the body.

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Antiviral Drugs

Drugs that target viral replication without harming host cells.

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Prions

Proteinaceous infectious particles that cause degenerative diseases.

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Mad Cow Disease

Bovine spongiform encephalopathy; a prion disease in cattle.

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MMR Vaccine

A vaccine that protects against measles, mumps, and rubella.

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What are viruses?

Acellular structures that require living host cells to reproduce. They are considered obligate parasites.

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How do viruses differ in structure?

Viruses can have diverse shapes, such as helical, spherical, polyhedral, or more complex forms.

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What are the key components of a virus?

Viruses consist of a capsid, an outer protein shell, and a nucleic acid core containing DNA or RNA. Some viruses may also have a lipid envelope.

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What is reverse transcriptase?

An enzyme found in retroviruses that converts RNA into DNA, allowing the virus to integrate its genetic material into the host cell's genome.

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How do viruses reproduce?

Viruses replicate by using the host cell's machinery and resources to create new viral particles.

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What is latency in a virus?

Some viruses can remain dormant within a host cell, sometimes for long periods, without causing any symptoms.

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What is a bacteriophage?

A virus that specifically infects bacteria.

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How are viruses specific to their hosts?

The spikes on a virus fit perfectly with receptor molecules on the membrane of a potential host cell, ensuring the virus infects the right type of cell.

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What are prions?

Misfolded proteins that can cause other proteins to misfold, leading to the accumulation of these misfolded proteins and various diseases.

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What are viroids?

Small, infectious strands of RNA that can replicate within a cell, causing disease in plants.

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Measles: Contagiousness

Measles spreads easily through the respiratory route.

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Measles: Incubation Period

The time between infection and the appearance of measles symptoms is 7 to 12 days.

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Measles: Mortality Rate

Measles can be fatal, especially in developing countries, where the fatality rate is 10-15%.

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Herpesviruses: Latency

Herpesviruses can remain inactive (latent) in the body for long periods.

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Herpes Simplex Type 1

This herpesvirus causes cold sores and fever blisters.

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Herpes Simplex Type 2

This herpesvirus causes genital herpes.

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Antiviral Drugs: Difficulty

Developing antiviral drugs is difficult because viruses use the host cell's machinery.

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Antiviral Drugs: Target

Antiviral drugs can target viral enzymes involved in replication.

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Measles Transmission

Measles spreads easily through the air, mainly through respiratory droplets.

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Measles Fatality Rate

Measles can be dangerous, especially in less developed countries, with a 10-15% fatality rate.

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What are Herpesviruses?

A group of viruses that can remain dormant (latent) in the body for long periods.

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Antiviral Drug Challenge

It's difficult to develop drugs that target viruses without harming the host's cells

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How do Antiviral Drugs work?

Some antiviral drugs can inhibit viral enzymes involved in replication.

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Viral Capsid

The protein shell that encloses a virus's genetic material (DNA or RNA). It protects the genome and helps the virus attach to host cells.

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Viral Envelope

A lipid membrane derived from the host cell that surrounds some viruses. It helps the virus evade the host's immune system.

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Viral Latency

A dormant state where a virus remains inactive within a host cell without producing new virus particles. It helps viruses evade the host's immune system.

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Bacteriophage

A virus that specifically infects bacteria. It uses the bacterial cell's machinery to reproduce.

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What are the main components of a virus?

Viruses consist of a capsid (protein shell) and a nucleic acid core (DNA or RNA). Some viruses may also have a lipid envelope.

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Why are viruses specific to hosts?

Viruses have spikes that fit perfectly with receptor molecules on the surface of host cells. This ensures the virus can only infect specific cell types.

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Study Notes

Viruses

  • Viruses are acellular structures that require a living cell to reproduce. They are obligate parasites.
  • Viruses use the host cell's machinery, like ribosomes and enzymes, for replication.
  • Viruses are smaller than bacteria, ranging from 0.03 to 0.2 micrometers.
  • Viral shapes vary, including helix, sphere, polyhedron, and more intricate forms.
  • Two key components of viruses are the capsid (outer protein layer) and the nucleic acid core (DNA or RNA).
  • Some viruses have a lipid envelope surrounding the capsid and spikes for attachment to host cells.
  • Viral genomes can be single- or double-stranded DNA or RNA.
  • Viruses infect almost all organisms, including bacteria (bacteriophages), plants, animals, and humans.
  • Host specificity means viruses only infect particular types of organisms.
  • Attachment to host cells occurs when spikes on the virus match receptor molecules on the host cell membrane.
  • The reproductive cycle typically has six steps in enveloped animal RNA viruses: attachment, entry, replication, biosynthesis, assembly, and budding.
  • Some viruses remain dormant (latent) within a host cell, helping them avoid detection by the immune system.
  • Examples of latent viruses include herpesviruses and retroviruses.
  • Retroviruses use reverse transcriptase to convert RNA to DNA (cDNA).
  • cDNA can be incorporated into the host cell genome, becoming a provirus, which is resistant to antiviral medications.
  • Common cold and influenza are caused by different viruses, with rhinoviruses responsible for colds and influenza viruses responsible for the flu.
  • Viral antigens can change over time.
  • Antigenic drift is small changes in viral surface proteins.
  • Antigenic shift is major changes, involving reassortment of viral genes, which can create new viral strains.
  • Measles is a highly contagious disease spread via respiratory routes.
  • Herpesviruses remain latent in the body and can cause diseases like cold sores, genital herpes, chickenpox, shingles, and infectious mononucleosis.
  • Antiviral drugs hinder viral replication by targeting viral enzymes or affecting attachment or assembly.
  • Antibiotics are not effective against viruses.

Viroids and Prions

  • Viroids and prions are acellular pathogens.
  • Viroids are naked, circular RNA molecules that do not code for proteins.
  • Viroids are smaller than most viral genomes and infect only plant cells.
  • Examples include potato spindle tuber and apple scar skin.
  • Prions are proteinaceous infectious particles. They cause normal proteins to change shape, leading to degenerative diseases of the nervous system.
  • Prions can be passed through the ingestion of infected tissue.
  • Examples include scrapie (sheep), bovine spongiform encephalopathy ("mad cow disease"), Creutzfeldt-Jakob disease (humans), Kuru (human-to-human transmission through cannibalism), and chronic wasting disease (deer, elk, and moose).

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BIO-121 Lab 12 - The Viruses PDF

Description

Explore the fascinating world of viruses with this quiz. Learn about their structure, replication process, and the role they play in various life forms. Test your knowledge on viral shapes, components, and host specificity in this informative quiz.

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