Virology: Structure, Genetics, and Classification
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Questions and Answers

What is the primary function of a virus's protein coat (capsid)?

  • To protect the virus from antibiotics.
  • To provide the virus with energy (ATP).
  • To facilitate the virus's entry into a host cell. (correct)
  • To store the virus's genetic material for replication.

Which of the following is a characteristic that viruses share with living organisms?

  • The ability to generate energy (ATP).
  • The ability to reproduce independently.
  • The presence of genetic material (DNA or RNA). (correct)
  • The presence of a cellular structure.

How do retroviruses introduce their genetic material into a host cell's DNA?

  • By directly replicating within the host cell's ribosomes.
  • By converting viral RNA into DNA using reverse transcriptase. (correct)
  • Through the creation of a protein coat around the viral DNA.
  • Through direct insertion of viral RNA.

Which of the following is a method of viral classification?

<p>Morphology and structure. (A)</p> Signup and view all the answers

What distinguishes the lysogenic cycle from the lytic cycle in viral replication?

<p>The lysogenic cycle involves a dormant phase where viral DNA integrates into the host's DNA. (A)</p> Signup and view all the answers

A virus with a 'head and tail structure' is most likely to infect which type of organism?

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

What is the primary mechanism by which vaccines provide protection against viral infections?

<p>By stimulating the immune system to recognize and respond to the virus. (D)</p> Signup and view all the answers

Which characteristic is exclusive to carcinogenic viruses?

<p>The capacity to cause irreparable genetic damage. (D)</p> Signup and view all the answers

Which factor determines if a latent virus will enter the lytic cycle?

<p>Conditions favorable for viral replication, such as a weakened immune system. (A)</p> Signup and view all the answers

Why are antibiotics ineffective against viral infections?

<p>Viruses lack the structures and metabolic processes that antibiotics target in bacteria. (D)</p> Signup and view all the answers

What is the essential requirement for a virus to proliferate?

<p>Infecting a living host for reproduction (C)</p> Signup and view all the answers

Viruses can contain both DNA and RNA as their genetic material.

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

What is the primary function of the viral capsid?

<p>The capsid protects the genetic material and facilitates entry into the host cell.</p> Signup and view all the answers

Viruses that have a structure with a head and tail specifically infect ________.

<p>bacteria</p> Signup and view all the answers

Match the virus type with its characteristic structure:

<p>Helical Virus = Has RNA, capsomere of capsid Enveloped Virus = Membranous envelope, RNA, Capside, Glycoprotein Virus with head and tail = Can only infect bacteria</p> Signup and view all the answers

Which of the following is NOT a characteristic of non-living viruses?

<p>Presence of metabolic activity (C)</p> Signup and view all the answers

Viral classification is solely based on the type of host they infect.

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

What is the role of mRNA in the viral replication process?

<p>mRNA is required for viral replication, and it can be translated by ribosomes</p> Signup and view all the answers

The release of new viruses from a host cell by causing it to burst is known as ________.

<p>lysis</p> Signup and view all the answers

Match the viral infection type with its description:

<p>Lytic Cycle = Viral replication leading to host cell destruction Lysogenic Cycle = Viral DNA integrates into the host's DNA and remains inactive for a period Persistent Infection = Virus stays inside and make the cell stick Latent Infection = Viruses closes nucleus and integrates with you genome</p> Signup and view all the answers

What is the function of reverse transcriptase in retroviruses?

<p>To convert viral RNA into DNA (D)</p> Signup and view all the answers

Antibiotics are an effective treatment against viral infections.

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

Describe a carcinogenic virus.

<p>It is a virus which can cause irreparable genetic damage once in the cell causing cancer.</p> Signup and view all the answers

Viruses that remain inactive inside a host cell for an extended period exhibit ________ infection.

<p>latent</p> Signup and view all the answers

Match the term with its role in preventing or treating viral infections:

<p>Antivirals = Prevent virus infecting cells Vaccines = Introduce the immune system to viral recognition signals Immune System = Rest and antioxidants</p> Signup and view all the answers

Which of the following is a common mode of transmission for viral diseases?

<p>Physical contact or sexual contact (A)</p> Signup and view all the answers

A virus in the lysogenic cycle always immediately destroys the host cell.

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

Why viruses are considered non-living outside the host cell?

<p>Viruses are considered non-living because they lack essential characteristics of life, such as metabolism and independent reproduction.</p> Signup and view all the answers

The genetic material of a virus can be either DNA or ________.

<p>RNA</p> Signup and view all the answers

Match the term with its definition:

<p>Capsid = Protein coat that encases the genetic material of a virus Retrovirus = Virus that uses reverse transcriptase to convert RNA into DNA Lysis = The breaking down of a cell</p> Signup and view all the answers

What is the primary target of antiviral drugs?

<p>Specific viral enzymes or proteins (C)</p> Signup and view all the answers

Viruses can infect any type of cell, including bacteria, plants, and animals.

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

What is the role of vaccines in preventing viral infections?

<p>Vaccines prepare the immune system of the body, offering protection from viral recognition signals</p> Signup and view all the answers

Viruses are classified based on their morphology, genetic composition, and ________.

<p>pathology</p> Signup and view all the answers

Match the way of getting infected with its description.

<p>Bites = Transmission through animal bites Air/Environmental Exposure = Indirect contact through contaminated surfaces or air Mother to child = Transmission during pregnancy, childbirth, or breastfeeding</p> Signup and view all the answers

Which of these best describes a 'pathogenic' virus?

<p>It can only reproduce if attacking another cell (D)</p> Signup and view all the answers

Viruses are capable of independent growth and development outside of a host cell.

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

Explain why viruses are not considered cells.

<p>Viruses lack the fundamental components of a cell. They are considered non-cellular structures, not organisms.</p> Signup and view all the answers

Enveloped viruses, such as the influenza virus, possess a ________ derived from the host cell membrane.

<p>membranous envelope</p> Signup and view all the answers

Relate the following terms to the example:

<p>Helical = Tobacco mosaic virus Enveloped = Influenza virus Structure with head and tail = Can only infect bacteria</p> Signup and view all the answers

Consider a scenario where a virus integrates its DNA into the host cell's genome but does not immediately cause harm. Which type of infection is this?

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

All viruses are deadly.

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

What common characteristic is observed in both living organisms and viruses?

<p>Both contain organization!!!</p> Signup and view all the answers

The process by which a virus uses special enzymes to attack another cell unless they reproduce is referred to as ________.

<p>pathogenic</p> Signup and view all the answers

Associate the following terms with their definitions.

<p>Reproduction = In host Genetic Material = RNA/DNA</p> Signup and view all the answers

If a virus has caused irreparable genetic damage, what kind of virus is it?

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

Viruses can produce ATP

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

True or False: Viruses are able to grow and develop on their own.

<p>False</p> Signup and view all the answers

All viruses must make ______ to translate by hot ribsomes.

<p>mRNA</p> Signup and view all the answers

Match the step to the cycle:

<p>Lytic Cycle = Cell bursts open releasing new viruses Lysogenic Cycle = Viral DNA inserts itself into hosts DNA</p> Signup and view all the answers

Which type of virus would you classify a virus that closes a nucleus and integrates with your genome?

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

Flashcards

What is a Virus?

Infectious particle with DNA or RNA, needs a host to reproduce and can affect genes.

What is a Capsid?

The outer protein coat of a virus, essential for entering host cells.

What is the goal of a virus?

Viruses must produce mRNA that can be translated by ribosomes to make more viruses.

How are viruses similar to living organisms?

Viruses have genetic material (RNA/DNA), can reproduce inside a host, and have organization to make viral proteins.

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How are viruses classified?

Includes morphology, infected organisms, genetic composition, and pathology.

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What is lysis?

The breaking of a cell due to viral infection.

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What happens in the Lysogenic cycle?

Integrates its DNA into the host cell's genome.

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What is Reverse Transcriptase?

Enzyme that converts viral RNA to DNA, allowing integration into the host's genome.

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Do antibiotics work on viruses?

Do not work against viruses; antivirals are used instead which prevent viruses from infecting cells.

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What is the role of vaccines?

Taken beforehand to prevent infection and introduce the immune system to viral recognition signals.

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Persistent Viral Infection

A virus that stays inside and makes the infected cell stick to other cells.

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Latent Viral Infections

A dormancy period where viruses close the nucleus and integrate their genome with yours.

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Retroviruses

Viruses that use reverse transcriptase to convert RNA to DNA.

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Lytic vs. Lysogenic Cycle

Breaks open the infected host cell. or integrates with the host cell

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Steps of the Lytic Cycle

Viral DNA is injected into host cell, host cell replicates and assembles new viruses, cell bursts releasing the viruses

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Steps of the Lysogenic Cycle

A viral infection in which the virus injects its DNA into host cell and inserts it into the DNA and remains inactive.

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Transmission of Viral Diseases

Infections through bites, sexual contact, bodily fluids, or air exposure.

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Pathogenic (Viruses)

Cannot reproduce unless they attack another cell

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Carcinogenic (Viruses)

causes irreparable damage -> tumors/ Cancers

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Antivirals

Specific drugs that prevent virus from infecting cells.

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Study Notes

  • Viruses are infectious particles containing either DNA or RNA, and must infect a living host to reproduce
  • Viruses can affect genes

Virus Structure

  • Genetic Material (inside): single-stranded RNA, double-stranded RNA, single-stranded DNA, or double-stranded DNA
  • Protein Coat (outside): capsid, which is key to entering a cell

Viral Genetics

  • All viruses must create mRNA that is translated by host ribosomes to make more viruses

Living vs. Non-living

  • Viruses are non-living because they lack cells, don't respond to stimuli, have no energy (ATP), don't grow or develop, and cannot reproduce on their own
  • Viruses are similar to living organisms because they have genetic material (RNA/DNA), reproduce in a host, and are organized to make viral proteins

Virus Classification

  • Viruses are grouped/classified by morphology (shape/structures), what they infect (plants, animals, bacteria), genetic composition (DNA, RNA, single or double-stranded), and pathology/nature of disease (deadly, inconvenient, highly contagious, or not)

Virus Structures

  • Some viruses with a head and tail structure can only infect bacteria
  • Helical viruses (like Tobacco mosaic Virus) possess RNA and a capsomere of capsid
  • Enveloped viruses (like Influenza Virus) have a membranous envelope, RNA, capside, and glycoprotein

Viral Infections

  • A viral infection can result in lysis (break) of cells
  • Persistent infections occur when a virus stays inside and makes the cell sticky
  • Latent infections occur when a virus closes into the nucleus and integrates with the host genome

Retroviruses

  • Retroviruses can convert RNA to DNA using the special enzyme Reverse Transcription
  • This DNA can disrupt your genomic DNA

Viral Replication

  • Lytic Cycle: breaks open the host cell
  • Lysogenic Cycle: virus integrates with the host cell; a virus can switch between cycles

Lytic Cycle Steps

  • Viral DNA is injected into a host cell
  • The host cell replicates viral DNA and makes the viral capsid (protein coat)
  • New viruses are assembled inside the host cell
  • The cell bursts open, releasing new viruses

Lysogenic Cycle Steps

  • Viral DNA is injected into the host cell
  • Viral DNA inserts itself into the host's DNA
  • The viral DNA remains inactive for days, months, or years
  • As the cell reproduces, more cells are produced that have the viral DNA in them
  • Eventually, when conditions are favorable (like when your immune system is weakened), the virus will enter the lytic cycle

Transmission of Viral Disease

  • Ways to get infected: bites, physical/sexual contact, body fluid, mother to child, contact in air/environmental exposure
  • Pathogenic viruses cannot reproduce unless they attack another cell
  • Carcinogenic viruses cause irreparable genetic damage and cancer once inside a cell (e.g., HPV and cervical cancer and Hepatitis B & C & liver cancer and T-lymphotropic & leukemia)

Virus Treatment

  • Antibiotics do NOT work on viruses
  • Antivirals are specific for infections and prevent viruses from infecting cells (e.g., Tamiflu, Relenza)
  • A strong immune system with rest and antioxidants can fight virus
  • Vaccines are taken beforehand to prevent infection and start by introducing the immune system to viral recognition signals

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Description

Explore the structure of viruses, including their genetic material (DNA or RNA) and protein coat. Learn about viral genetics, the distinction between living and non-living characteristics of viruses, and how viruses are classified based on morphology, host, and genetic composition.

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