Virology: Capsid Structure and Transmission

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Questions and Answers

What is the term for the large, multinucleated cell that forms as a result of viral infection?

Macrophage

Syncytium (correct)

Fibroblast

Neutrophil

Which virus is classified as a retrovirus?

Marburg virus

Ebola virus

HIV (correct)

Rabies virus

What is a characteristic of virion numbers inside a cell during phase 4 of the viral growth curve?

They diminish over time due to cellular defense

They can exponentially increase without limit

They stabilize at a constant number of 1,000

They are restricted to 100-10,000 per cell (correct)

Which statement about viruses is true?

Viruses have a capsid that is present in all types Signup and view all the answers

What distinguishes hepatitis B virus from other DNA viruses in terms of replication?

It utilizes reverse transcriptase in its replication Signup and view all the answers

What is the primary function of the protein coat in a virus?

It encloses the viral genome. Signup and view all the answers

Which type of virus symmetry consists of 20 flat sides?

Icosahedral Signup and view all the answers

Which mode of virus transmission is exemplified by HIV?

Direct contact Signup and view all the answers

Which viral structure is characterized by its spiral or cylindrical shape?

Helical Signup and view all the answers

What type of virus cannot withstand gastric acidity?

Enveloped viruses Signup and view all the answers

What is the role of inserted viral proteins like peplomers?

To enhance immune response and attachment. Signup and view all the answers

Which virus is an example of a complex symmetry type?

Rabies virus Signup and view all the answers

What type of nucleic acid is characteristic of helical enveloped viruses?

Single-stranded RNA Signup and view all the answers

Which of the following characteristics distinguishes viruses from living organisms?

Viruses are considered acellular. Signup and view all the answers

Which of the following viral families contains double-stranded DNA viruses?

Hepadnaviridae Signup and view all the answers

What is a defining feature of viruses regarding their energy production?

Viruses require a host for energy production. Signup and view all the answers

Which microscopy technique can demonstrate viruses directly?

Transmission Electron Microscopy Signup and view all the answers

Which of the following virus families is known for containing single-stranded DNA viruses?

Parvoviridae Signup and view all the answers

Which statement correctly describes the classification of Hepatitis B virus?

It is a double-stranded DNA virus with reverse transcriptase. Signup and view all the answers

What is a common feature of viruses regarding their dependence on host cells?

They are obligate intracellular parasites. Signup and view all the answers

What differentiates the methodologies used for gram-staining from those used for visualizing viruses?

Gram-staining uses visible light to magnify images. Signup and view all the answers

What type of genome does Group II viruses, such as Parvovirus B19, possess?

Single-stranded DNA Signup and view all the answers

During the replication of Group II ssDNA viruses, what is the first step in the conventional pathway?

Viral genome is manufactured Signup and view all the answers

Which polymerase is required to produce viral mRNA from the DNA negative strand in Group II replication?

DNA-dependent RNA polymerase Signup and view all the answers

In Group III dsRNA viruses, why can't the positive strand function as mRNA?

It is hydrogen bonded to the negative strand Signup and view all the answers

What type of enzyme do some Group V ssRNA viruses require to replicate?

Their own RNA polymerase Signup and view all the answers

Which of the following families belongs to Group II viruses?

Parvoviridae Signup and view all the answers

What is the end result of the replication process for Group II ssDNA viruses?

Double-stranded DNA replicative form Signup and view all the answers

In the Baltimore Classification system, which group does ssDNA (+) belong to?

Group II Signup and view all the answers

Which RNA virus family contains viruses that are classified as enveloped helical?

Arenaviridae Signup and view all the answers

Which of the following RNA virus families includes rotavirus?

Reoviridae Signup and view all the answers

Which virus is an example of the Retroviridae family?

HIV Signup and view all the answers

What type of virion is associated with the Flaviviridae family?

Enveloped icosahedral Signup and view all the answers

Which group does the Paramyxoviridae family belong to?

Grp 4 Signup and view all the answers

Study Notes

Capsid Structure and Function

A protein coat that encloses the viral genome.
Three types of symmetry in viral capsids:
- Icosahedral: Polyhedral with 20 flat sides; commonly found in DNA and (+) sense RNA viruses.
  - Naked icosahedral virus lacks an envelope.
  - Enveloped icosahedral virus has its genome inside an envelope.
- Helical: Spiral or cylindrical shape forming a helix; includes enveloped (-) sense RNA viruses.
  - Naked helical virus features a coiled nucleocapsid.
  - Enveloped helical virus is inside an envelope.
- Complex: Lacks regular symmetry; includes Poxvirus (dumbbell-shaped) and Rabies virus (bullet-shaped).

Virus Characteristics

Viruses are acellular and lack organelles and metabolic processes, distinguishing them from living organisms.
They are submicroscopic and cannot be visualized using optical microscopes; typically detected through gram-staining.
Considered obligate intracellular parasites, requiring host cells for replication.

Viral Transmission Modes

Direct Contact: e.g., HIV transmission.
Feco-oral Route: e.g., Poliovirus transmission.

Viral Genome Classification (Baltimore Classification)

Group I: dsDNA (e.g., Adenoviridae, Poxviridae, Herpesviridae).
Group II: ssDNA (+), with Parvoviridae as the only family (e.g., Parvovirus B19).
Group III: dsRNA, which cannot serve as mRNA due to hydrogen bonding with the negative strand.
Group IV: ss(+)RNA, requires its own RNA polymerase for replication.
Group V: ss(-)RNA, uses the negative strand as a template for mRNA synthesis.

Viral Replication Process

Replication involves various phases, notably during Phase 2.
ssDNA viruses follow conventional pathways: DNA → mRNA → protein formation.
All viruses contain a capsid, crucial for protecting genetic material and aiding in infection.

Pathological Effects of Viruses

Viral infections can lead to the formation of syncytia, multinucleated giant cells formed by the fusion of infected cells.
Examples of retroviruses include HIV and other similar pathogens.

Categories of Viruses (Examples)

Naked Icosahedral: Caliciviridae (Norwalk), Reoviridae (Rotavirus).
Enveloped Icosahedral: Retroviridae (HIV), Flaviviridae (Dengue).
Enveloped Helical: Coronaviridae (SARS-CoV), Rhabdoviridae (Rabies), Filoviridae (Ebola).

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Description

This quiz covers essential concepts related to the structure and function of the capsid in viruses. It includes details on the protein coat, modes of transmission, and the impact of environmental factors. Test your knowledge on how these elements contribute to viral behavior.