Virology Overview and Characteristics

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Questions and Answers

What unique characteristic distinguishes viruses from all other microorganisms?

Presence of ribosomes

Contain DNA or RNA

Lack of cellular structure (correct)

Ability to replicate independently

Which type of viral genome is an exception by being single-stranded but still considered double-stranded?

Reoviruses

Parvoviruses (correct)

Cubic symmetry viruses

Retroviruses

What is the primary function of the viral capsid?

To serve as the viral envelope

To replicate viral genome

To facilitate the release of new virions

To protect the nucleic acid (correct)

Which type of symmetry is characterized by viruses like adenovirus and herpesvirus?

Cubic symmetry Signup and view all the answers

What is the first step in the viral replication process?

Adsorption (Attachment) Signup and view all the answers

What refers to the combination of a genome and a capsid in a virus?

Nucleocapsid Signup and view all the answers

Which viral component is derived from the cell membrane during the process of budding?

Envelope Signup and view all the answers

Which type of viral release involves the rupture of the host cell?

Lysis Signup and view all the answers

Which of the following viruses is known for having complex symmetry?

Poxviruses Signup and view all the answers

During the synthesis stage of viral replication, what is produced from the viral genome?

mRNA and enzymes Signup and view all the answers

What method would be least effective for diagnosing viral infections at the molecular level?

Microscopic examination Signup and view all the answers

Which class of viruses contains reverse transcriptase as part of their structure?

Retroviruses and HBV Signup and view all the answers

What makes enveloped viruses more susceptible to environmental factors compared to non-enveloped viruses?

Lipoprotein membrane Signup and view all the answers

What role do cell ribosomes play in the viral replication cycle?

Translation of viral mRNA into proteins Signup and view all the answers

Which of the following statements is true about the nucleic acid in viruses?

All viruses are haploid except retroviruses which are diploid. Signup and view all the answers

Which cellular structure is primarily involved in the assembly of new virions?

Cytoplasm Signup and view all the answers

What is a characteristic feature of inclusion bodies associated with viral infections?

They can appear as 'Owl’s eye' in cases of CMV infection. Signup and view all the answers

What best describes the final outcome after viral assembly in the replication cycle?

The virus is released through budding or lysis. Signup and view all the answers

Which type of viruses typically undergo budding during the release stage of the viral replication cycle?

Enveloped viruses Signup and view all the answers

During which stage of viral replication does the viral genome undergo transcription to produce mRNA?

Synthesis Signup and view all the answers

What characteristic distinguishes whether a virus is enveloped or nonenveloped?

The presence of a lipid membrane Signup and view all the answers

Which of the following viruses is classified as double-stranded DNA?

Adenoviridae Signup and view all the answers

During which step of the viral replication cycle does the viral envelope fuse with the host cell membrane?

Penetration Signup and view all the answers

What is the role of glycoproteins in the viral life cycle?

They serve as attachment sites to host cells. Signup and view all the answers

Which process describes the release of new viral particles from an infected host cell?

Budding Signup and view all the answers

What type of symmetry do nonenveloped icosahedral viruses exhibit?

Icosahedral Signup and view all the answers

Which viral family is known for its segmented RNA genome?

Reoviridae Signup and view all the answers

Which type of viral genome is typically not found in RNA viruses?

Reverse-transcribed Signup and view all the answers

Which step follows the uncoating of the viral genome during replication?

Synthesis of viral components Signup and view all the answers

What type of nucleic acid is characteristic of retroviruses?

Single-stranded RNA Signup and view all the answers

Which type of cell culture is characterized by continuous growth and immortality?

Continuous Cell Line Signup and view all the answers

What issue is NOT associated with traditional cell culture methods?

High sensitivity to all viruses Signup and view all the answers

Which virus is known for not growing in cell culture?

Human Papillomavirus (HPV) Signup and view all the answers

Which serological test method is based on detecting antibodies?

Enzyme-linked Immunosorbent Assay (ELISA) Signup and view all the answers

What does the shell vial assay primarily detect?

Viral Antigens Signup and view all the answers

Which of the following viruses is most sensitive to the HEp-2 cell line?

Respiratory Syncytial Virus (RSV) Signup and view all the answers

What is the role of Polymerase Chain Reaction (PCR) in viral testing?

Amplifying nucleic acid for detection Signup and view all the answers

Which method involves direct detection of antigens in a sample?

Direct Immunofluorescence Signup and view all the answers

What type of viral growth detection shows effects such as cell rounding and syncytium formation?

Cytopathic Effects Signup and view all the answers

Which of the following viruses is categorized as an RNA virus with high sensitivity in primary monkey kidney (PMK) cell cultures?

Rhinovirus Signup and view all the answers

Study Notes

Objectives of Study

Distinguish viruses from other microorganisms.
Understand general characteristics, structure, classification, and replication of viruses.
Learn methods for laboratory diagnosis of viral infections.

Properties of Microorganisms

Parasites, fungi, and bacteria are cellular; viruses are acellular.
Organisms classified as:
- Parasites: Eukaryotic cells with nuclei.
- Fungi: Eukaryotic cells with nuclei.
- Bacteria: Prokaryotic cells without true nuclei.
- Viruses: Lack cellular structure.
Viruses have either DNA or RNA, while other microorganisms can have both.

Characteristics of Viruses

Consist of tiny particles with an internal core, a protein coat, and sometimes a lipoprotein membrane.
Obligate intracellular organisms that replicate uniquely.
Size ranges from 20-300 nm.

Viral Structure

Viral Genome: Can be DNA (ds or ss) or RNA (ss or ds).
Capsid: Protein coat made of capsomeres, protects nucleic acid, assists in entry into host cells.
Envelope: Lipoprotein membrane derived from host cell; increases sensitivity to environmental factors.

Symmetry of Virus Structure

Cubic Symmetry (Icosahedral): Common in adenovirus and herpesvirus.
Helical Symmetry: Found in elongated viruses like filoviruses and pleomorphic influenza virus.
Complex Symmetry: Seen in poxviruses.

Viral Proteins

Outer Proteins: Aid in attachment to host receptors, induce neutralizing antibodies.
Internal Proteins: Include structural proteins (capsid) and nonstructural proteins (enzymes).
ssRNA viruses often have RNA-dependent RNA polymerase; retroviruses contain reverse transcriptase.

Classification of Viruses

Based on nucleic acid type, strand number, polarity, presence of an envelope, and type of symmetry.
Medically important viruses categorized as DNA (single/double-stranded, enveloped/nonenveloped) and RNA (negative/positive-stranded, enveloped/nonenveloped).

Viral Replication Cycle

Steps:
- Adsorption (Attachment)
- Penetration
- Uncoating
- Synthesis of viral components (mRNA, viral proteins, nucleic acid)
- Assembly
- Release (via budding or cell lysis)

Laboratory Diagnosis of Viral Infections

Methods include:
- Microscopic examination to identify inclusions and morphology.
- Cell culture techniques to isolate viruses.
- Serological tests to detect viral antigens or antibodies.
- Molecular methods like PCR for viral detection.

Microscopic Examination

Light microscopy reveals histological features such as viral inclusion bodies.
Electron microscopy provides detailed morphology and size of virions, useful in diagnosing specific infections.

Virus Cultivation Methods

Laboratory animals, embryonated eggs, and various cell culture types (primary, diploid, continuous).

Sensitivity of Cell Cultures

Varies among clinical virology laboratory isolated viruses, impacting detection and growth properties.

Problems with Cell Culture Techniques

Long incubation periods, variable sensitivity, risk of bacterial contamination, and certain viruses not growing in culture (e.g., HPV).

Rapid Culture Techniques

Shell Vial Assay: Detects viral antigens quickly (1-3 days).

Serological Tests for Viral Detection

Differentiation between antigen and antibody detection using techniques like immunofluorescence and ELISA.

Immunofluorescence Techniques

Direct and indirect approaches to detect antigens or antibodies in samples.

Molecular Testing

PCR amplifies viral nucleic acid, providing sensitive detection of viral infections.

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Description

This quiz focuses on the essential aspects of virology, including the distinction between viruses and other microorganisms, their structure, classification, and replication. Additionally, it covers laboratory methods for diagnosing viral infections. Test your understanding of these crucial topics in microbiology!