أسئلة السابعة ميكرو دمياط (قبل التعديل)
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Questions and Answers

What is a consequence of transcriptional errors in viruses?

  • Decreased virion production
  • Inhibition of viral protein assembly
  • Formation of viral inclusion bodies
  • Introduction of new mutants with clinical importance (correct)

Which process may contribute to the release of virus particles from infected cells?

  • Budding from the cell surface (correct)
  • Membrane fusion with neighboring cells
  • Cell wall rupture
  • Intracellular digestion

What type of test is primarily used to assess an acute viral infection?

  • Histopathological tests
  • Antibody detection tests
  • Antigen detection tests (correct)
  • Latent infection tests

What characterizes latent viral infections, such as those caused by herpes viruses?

<p>Viral genome present without cell damage (B)</p> Signup and view all the answers

Which method is commonly used to detect viral antigens in samples?

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

What occurs during the lysis of an infected cell?

<p>Release of intact infectious virions (D)</p> Signup and view all the answers

What is one of the roles of viral vaccines?

<p>Prevention of viral infections (D)</p> Signup and view all the answers

What can happen to cells infected by certain viruses over time?

<p>They may transform into tumor cells (C)</p> Signup and view all the answers

What is the primary definition of a virus?

<p>A sub-microscopic obligate intracellular parasite (D)</p> Signup and view all the answers

What is the function of envelope glycoproteins on a virus?

<p>To facilitate attachment to target cells (D)</p> Signup and view all the answers

What term describes the protein shell that surrounds the nucleic acid of a virus?

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

Which type of nucleic acid may a virus contain?

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

What is required for viral penetration into a host cell?

<p>Metabolic activity of the host cell (C)</p> Signup and view all the answers

Which statement correctly describes early and late viral proteins?

<p>Early proteins are produced before DNA or RNA replication (C)</p> Signup and view all the answers

How do viruses replicate if they have RNA genomes?

<p>They require their own polymerases to replicate (A)</p> Signup and view all the answers

Which mechanism is NOT involved in viral penetration into host cells?

<p>Passive diffusion through the cell membrane (D)</p> Signup and view all the answers

What distinguishes antiviral drugs from antibiotics?

<p>Antiviral drugs specifically target viral infections. (A)</p> Signup and view all the answers

Which of the following is NOT an example of an antiviral agent?

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

Why do we need different influenza vaccines each year?

<p>Influenza viruses mutate quickly. (C)</p> Signup and view all the answers

What is a common source of influenza infection?

<p>Airborne droplets from coughs and sneezes (A)</p> Signup and view all the answers

Which of the following statements about viruses is true?

<p>Viruses can contain either DNA or RNA as their genetic material. (B)</p> Signup and view all the answers

Which type of vaccine is considered genetically engineered?

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

What is one major difference between viruses and bacteria?

<p>Viruses cannot survive without a host cell. (C)</p> Signup and view all the answers

Which of the following best describes a live attenuated virus vaccine?

<p>It contains weakened live virus that cannot cause disease. (B)</p> Signup and view all the answers

Which of the following drugs is NOT used for the treatment of viral infections?

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

What do we refer to when discussing infection prevention measures?

<p>Public health guidelines and hygiene practices (C)</p> Signup and view all the answers

What may occur if a virus causes a latent infection?

<p>Reactivate due to immune changes leading to virus production (A)</p> Signup and view all the answers

What is a significant reason for performing PCR or antigen detection tests?

<p>To assess acute infections (A)</p> Signup and view all the answers

How do some viruses exit the host cell without killing it?

<p>Through budding from the cell surface (A)</p> Signup and view all the answers

In which testing method would you find serum samples analyzed for specific antiviral antibodies?

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

What may potentially lead to the formation of inclusion bodies in viral infections?

<p>The accumulation of virions during assembly (C)</p> Signup and view all the answers

Which of the following methods is NOT used for antigen detection during viral diagnosis?

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

What distinguishes the common outcome of viral infections characterized by host cell damage versus those that lead to cell death?

<p>Progeny viruses are produced in cases of cell damage (D)</p> Signup and view all the answers

Which factor might contribute to the lack of virus progeny despite viral infection?

<p>Unique resistance of the infected cell (C)</p> Signup and view all the answers

What is the function of capsomers in a virus?

<p>They form the protein shell that encloses the nucleic acid. (C)</p> Signup and view all the answers

Which of the following statements about viral genomes is incorrect?

<p>Viral genomes are always linear in structure. (B)</p> Signup and view all the answers

What defines host species and cell tropism for viruses?

<p>The specificity of the reaction between viral proteins and host receptors. (D)</p> Signup and view all the answers

What is a key requirement for the active process of viral penetration?

<p>The target host cell's metabolic activity. (A)</p> Signup and view all the answers

Which statement best describes the characteristics of 'Early' viral proteins?

<p>They are commonly involved in the replication of viral nucleic acids. (A)</p> Signup and view all the answers

What does the nucleocapsid of a virus consist of?

<p>The combination of the capsid and its enclosed nucleic acid. (C)</p> Signup and view all the answers

What is the primary function of viral glycoproteins?

<p>To facilitate attachment to specific host cell receptors. (A)</p> Signup and view all the answers

Which type of polymerases do viruses with RNA genomes need?

<p>Viral polymerases which they must synthesize or bring. (C)</p> Signup and view all the answers

Which of the following antiviral agents is specifically indicated for the treatment of influenza?

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

What is the fundamental characteristic that differentiates viruses from bacteria?

<p>Viruses contain either DNA or RNA but not both. (D)</p> Signup and view all the answers

Which type of vaccine is least likely to elicit a cellular immune response?

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

Why is it necessary to develop a new influenza vaccine each year?

<p>Influenza virus mutations result in changed antigenic properties. (C)</p> Signup and view all the answers

Which of the following conditions is primarily caused by a virus?

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

Antiviral drugs are designed to target which of the following?

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

In the case of Grandfather Ali, which misconception did he address regarding flu treatment?

<p>The flu is caused by a virus, not a bacterium. (B)</p> Signup and view all the answers

What type of viral genome can be found in viruses?

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

Which of the following is likely to be a common source of influenza infection?

<p>Respiratory droplets from infected individuals (A)</p> Signup and view all the answers

What is a crucial reason for differentiating between antiviral drugs?

<p>Each antiviral drug has specific indications based on the virus type. (B)</p> Signup and view all the answers

Flashcards

Viral Release Mechanisms

How viruses exit infected cells. They can bud from the cell surface, use exocytosis, or cause cell lysis.

Inclusion Bodies

Clusters of viral particles within infected cells, often used in viral diagnosis.

Latent Infection

A type of viral infection where the virus remains hidden in the host cell without causing harm, but can be reactivated later.

Productive Infection

A viral infection where the virus replicates and produces new viruses, often causing cell damage.

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Viral Diagnosis Methods

Tests used to detect viral infections, including PCR for viral genome detection, antigen detection, and antibody detection.

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PCR and Antigen Tests

Used to diagnose acute viral infections. They detect the presence of the virus itself.

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Antibody Tests

Used to detect past exposure to a virus by looking for antibodies produced by the immune system.

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Viral Vaccination

A method to prevent viral infections by introducing weakened or inactive viruses into the body to stimulate an immune response.

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What are viruses?

Viruses are submicroscopic, obligate intracellular parasites that can only replicate inside living, dividing host cells.

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What is a virion?

A virion is a complete, infectious virus particle outside of a host cell. It consists of a nucleic acid core (DNA or RNA) encased in a protein shell called a capsid.

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What is an envelope?

An envelope is a membrane surrounding some viruses, derived from the host cell membrane.

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How do viruses attach to cells?

Viruses have specific proteins on their surface that bind to receptors on the surface of host cells.

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What is viral penetration?

Viral penetration is the entry of the virus into the host cell, often through endocytosis or fusion with the cell membrane.

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What is the role of viral polymerases?

Viral polymerases are enzymes that create new copies of the viral genome. They are essential for viral replication.

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What are early and late proteins?

Early proteins are produced first and often include enzymes like polymerases. Late proteins are produced later and are usually structural proteins like capsid and envelope proteins.

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How does viral replication occur?

Viral replication involves the use of host cell machinery to produce new viral genomes and proteins. The new viral components then assemble into new virions, which can go on to infect more cells.

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Antiviral Drugs

Medicines used to treat viral infections, aiming to control or cure them. Each drug has specific applications and limitations.

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Viruses vs. Bacteria

Viruses are much smaller than bacteria, lack organized cellular structures, and have a simpler genetic makeup (DNA or RNA). Bacteria are single-celled organisms with complex structures and have their own DNA.

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Influenza (Flu)

A contagious respiratory illness caused by influenza viruses. It manifests with symptoms like fever, cough, sore throat, runny nose, and muscle aches.

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Influenza Virus Types

There are different types of influenza viruses, primarily A, B, and C. Influenza A viruses are the most common and can cause severe outbreaks.

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Influenza Sources of Infection

Influenza spreads through respiratory droplets released when infected individuals cough, sneeze, or talk. These droplets can infect others if inhaled or land on their mucous membranes.

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Antiviral Agent Examples

Examples of antiviral drugs include Acyclovir (for herpes), Zidovudine (AZT) and Lamivudine (3TC) (for HIV), Protease inhibitors (for HIV), Tamiflu (for influenza), Sovaldi and daclatasvir (for hepatitis C), Remdesivir and Favipravir (for COVID-19).

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Seasonal Influenza Vaccine

A vaccine formulated annually to protect against the most prevalent influenza strains circulating during that specific season.

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Why Different Flu Vaccines Each Year?

Influenza viruses evolve and mutate constantly, producing new variants. Each year, scientists identify the most likely circulating strains and tailor the vaccine accordingly.

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Virus Culture and Isolation

Viruses can be cultured and isolated from pathological samples like blood, tissue samples, or respiratory swabs, to identify the specific virus causing illness.

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Viral Genomes

The genetic material of viruses can be either DNA or RNA. Some viruses have an envelope, a protective outer layer.

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What is the viral envelope?

The viral envelope is a protective outer layer surrounding some viruses, found in addition to the protein coat. It's made from the host cell membrane.

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What are 'early' viral proteins?

These proteins are produced first during infection. They typically include enzymes like polymerases, which are essential for making new viral genomes.

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What are 'late' viral proteins?

These proteins are produced later and are usually structural, like those that form the capsid or envelope. They're the virus's building blocks.

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Viral Release: Budding

A virus exits the cell by pushing its way out of the cell membrane, forming a bud that becomes a new viral particle.

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Viral Release: Exocytosis

The virus is packaged within a vesicle inside the cell, then this vesicle merges with the cell membrane, releasing the virus outside.

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Viral Release: Lysis

The virus replicates within the cell until it bursts, killing the cell and releasing new viruses.

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Viral Infection: Latent Infection

The virus hides within the host cell without causing harm, but can reactivate later.

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Viral Infection: Productive Infection

The virus replicates within the cell, producing new viruses and often causing cell damage or death.

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Viral Diagnosis: PCR

Detects specific viral DNA or RNA using a polymerase chain reaction technique.

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Viral Diagnosis: Antigen Detection

Detects the presence of viral proteins within a sample.

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Viral Diagnosis: Antibody Detection

Detects the presence of antibodies produced by the body in response to a viral infection.

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Viral Infections

Illnesses caused by viruses, which are microscopic entities that need host cells to reproduce. They can affect various organs and systems.

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Sources of Influenza Infection

Influenza spreads through respiratory droplets released when infected individuals cough, sneeze, or talk. These droplets can infect others if inhaled or land on their mucous membranes.

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Study Notes

General Virology

  • Viruses are defined as submicroscopic, obligate intracellular parasites that only replicate inside living host cells.
  • Virions (virus particles) do not grow or undergo division.
  • Viral structure includes a protein shell (capsid), containing the nucleic acid (RNA or DNA). Some viruses have an outer envelope made of lipids derived from host cells.
  • Viral shapes include helical, icosahedral, and complex.
  • Virus size varies significantly, from 15 to 300 nanometers.
  • Viral replication involves six key steps: adsorption, penetration, uncoating, replication, assembly, and release.
  • Viral infections can cause various effects on host cells, including lysis (host cell death), or converting them into a permanent infected state.
  • Viral infections are diagnosed by detecting viral genetic material (DNA or RNA) using PCR, identifying viral antigens, or by detecting antibodies against the virus.

Viral Replication

  • Viral replication occurs in six main stages:
  • Adsorption: Viruses attach to specific receptors on host cells.
  • Penetration: The virus enters the host cell. This involves translocation (movement across the cell membrane), endocytosis (entry in vesicles), or fusion (viral envelope merging with the cell membrane).
  • Uncoating: The viral genome is released from the capsid.
  • Replication: The viral genome is replicated, and viral proteins are synthesized either using viral or cellular polymerases.
  • Assembly: New viral particles are assembled. Sites of assembly may form inclusion bodies.
  • Release: The new viral particles are released from the host cell either by exocytosis (budding), or cell lysis.

Viral Classification

  • Viruses are classified based on their nucleic acid type (DNA or RNA), strandedness (single or double), linearity (linear or circular), and segmentations. This classification is crucial for understanding viral behavior and developing targeted treatments.

Viral Structure

  • Viruses consist of a genetic material (RNA or DNA) enclosed in a protein coat (capsid).
  • Some viruses have an additional outer envelope derived from the host cell membrane, which can be crucial for infecting new cells.
  • The capsid is composed of protein subunits called capsomeres.
  • The nucleic acid determines the virus' genetic properties.

Viral Replication Mechanisms

  • Translocation: The entire virion moves across the cell membrane.
  • Endocytosis: The virus enters the host cell membrane within vesicles.
  • Fusion: The viral envelope fuses with the cell membrane.

Effects of Viral Infections on Cells

  • Some viral infections result in host cell death and new virus production (lytic infections).
  • Some infections lead to a persistent state where host cells remain infected but are not necessarily killed, or they can cause chronic infections or tumors.
  • Certain viruses can exist in a latent state, where the viral genome remains inactive until a trigger activates replication.

Genomic Transcription & Translation

  • Mammalian genes only synthesize DNA & RNA in the nucleus; thus, viruses replicating in the cytoplasm must make their own polymerases to replicate and transcribe viral genes. This is a critical aspect of viral pathogenesis.
  • Messenger RNA is translated into viral proteins by host ribosomes, or the viral proteins might bring their own polymerases. The "early" proteins are often involved in replication and transcription, while "late" proteins are structural components of the new virions. This distinct timing of protein production is important.

Assembly

  • Viral proteins assemble into new viral particles inside the host cell.
  • Assembly sites may lead to the formation of inclusion bodies, which aid in diagnosing viral infections. These are visible aggregates of viral proteins inside infected cells.

Release

  • Viruses are released via exocytosis through host cell membrane, or cell lysis. Different release mechanisms have differing effects.

Prevention and Treatment

  • Vaccination is a key method for preventing viral infections, inducing immunity to specific viral types.
  • Antiviral drugs are available but they are highly specific to particular viruses and have limited uses.

Laboratory Diagnosis

  • Viral infections are diagnosed using different methods:
    • Detecting viral genome using PCR, offering high precision.
    • Detecting viral antigens.
    • Antibody detection to determine prior infection (used for chronic conditions or past exposure).

Clinical Case

  • Grandfather Ali exhibited symptoms suggestive of a viral infection (cold). The incorrect advice to use antibiotics is a crucial point about differentiating viral and bacterial infections. The need for accurate diagnosis before prescribing treatment is paramount.

Summary

  • Viruses are microscopic agents that cause human infections.
  • Viral genomes comprise DNA or RNA.
  • Viral replication requires host cell machinery, frequently with the viral genome being a template for other viral genes.
  • The replication cycle can lead to host cell death (lysis).
  • Diagnosis often involves detecting viral nucleic acids (PCR), antigens, or antibodies.
  • Prevention frequently utilizes vaccines.
  • Antiviral medicine exists but tends to be targeted to specific types of viruses.

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