Viral Taxonomy and Classification Quiz

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Questions and Answers

What is a distinguishing feature of viruses in terms of nucleic acid compared to cells?

Only contain RNA

Only contain DNA

Have few or no proteins

Contain both DNA and RNA (correct)

Which component is absent in viruses but present in cells?

Ribosomes

Enzymes

Proteins

Mitochondria (correct)

How do viruses typically multiply compared to cells?

Meiosis

Mitosis

Binary fission

Budding (correct)

Which type of virus has an envelope made of lipoprotein membrane?

Complex virus Signup and view all the answers

What is the role of virions in the life cycle of a virus?

Virus particle at any stage Signup and view all the answers

How are viroids different from viruses?

Smaller than a virus and infect only plants Signup and view all the answers

Which classification system was adopted by the International Committee on Taxonomy of Viruses in 1966?

Universal system of viral classification Signup and view all the answers

What is the genome type that DNA viruses and eukaryotic cells share in terms of mutation rates?

Very low mutation rates Signup and view all the answers

Which type of nucleic acid can be either linear or circular?

DNA only Signup and view all the answers

What does a virus with reduced pathogenicity mean?

Less ability to cause disease Signup and view all the answers

What is the typical mutation rate for RNA viruses compared to DNA viruses?

Higher mutation rate Signup and view all the answers

Which family of viruses is an exception to being haploid?

Retroviruses Signup and view all the answers

What is the main difference between viruses and cells?

Viruses cannot produce energy or synthesize proteins on their own, while cells can. Signup and view all the answers

Which component is found in some viruses but not in all?

Envelope Signup and view all the answers

How do viruses reproduce compared to cells?

Viruses replicate to produce hundreds of progeny, while cells divide to produce only two daughter cells. Signup and view all the answers

Which organelle is absent in viruses but present in cells?

Mitochondria Signup and view all the answers

What feature distinguishes viruses as obligate intracellular parasites?

Their reliance on host cells for energy and protein synthesis. Signup and view all the answers

Which statement accurately describes the genetic material found in viruses?

Some viruses contain DNA, some contain RNA, but not both in the same virus. Signup and view all the answers

What is antigenicity in the context of a virus?

The ability of a virus to induce an immune response Signup and view all the answers

Which component of a virus is responsible for recognizing and attaching to specific receptors on host cells?

Spike proteins Signup and view all the answers

In the context of viruses, what is recombination?

A process where two related viruses exchange genetic material during infection Signup and view all the answers

Which symmetry configuration involves capsomers arranged in 20 triangles?

Icosahedral Symmetry Signup and view all the answers

What is the composition of a capsid in a virus?

Individual pentameric or hexameric protein assembly Signup and view all the answers

Which viruses typically have an envelope derived from the host cell membrane?

Herpes and covid Signup and view all the answers

What is the function of the outer surface proteins (Spikes) on a virus?

Determine the viral species and serotype Signup and view all the answers

How does the presence of an envelope affect the stability of a virus?

Makes it more sensitive to heat, detergents, acid, alcohol, drying Signup and view all the answers

What is the primary role of non-structural proteins in a virus?

Expressed mainly in infected cells and have enzymatic functions Signup and view all the answers

What do capsid core proteins primarily do in a virus?

Protect the viral DNA or RNA from degradation by nucleases Signup and view all the answers

How do outer surface proteins (Spikes) contribute to viral infectivity?

Mediate specific viral attachment to host receptors Signup and view all the answers

What affects the transmission mode of enveloped viruses?

Sensitivity to heat, detergents, acid, alcohol, drying Signup and view all the answers

Study Notes

Virus Characteristics and Differences from Cells

Viruses consist of nucleic acids (either DNA or RNA) but lack the cellular structure and components required for metabolic processes found in cells.
Viruses do not contain ribosomes but cells possess these essential organelles for protein synthesis.
Viruses replicate by hijacking host cellular machinery, contrasting with cellular division processes like mitosis or meiosis.
Enveloped viruses are characterized by a lipoprotein membrane derived from the host cell membrane.
Virions are complete virus particles that facilitate the infection process by delivering the viral genome into host cells.

Viroids vs. Viruses

Viroids are distinct from viruses as they are smaller, lack a protein coat, and consist solely of a short strand of RNA, primarily affecting plants.

Taxonomy and Classification

The International Committee on Taxonomy of Viruses adopted a classification system in 1966 that categorized viruses based on properties like their nucleic acid type and replication strategies.

Mutation Rates and Genome Types

DNA viruses and eukaryotic cells share a common genome type, typically facing lower mutation rates compared to RNA viruses.
RNA viruses generally have higher mutation rates, significantly impacting viral evolution and adaptability.

Nucleic Acid Forms

Viral nucleic acids can be either linear or circular, offering various mechanisms for genetic replication and recombination.

Pathogenicity

A virus with reduced pathogenicity indicates a lower ability to cause disease, often due to mutations or adaptations.
The typical mutation rate for RNA viruses is significantly higher than that of DNA viruses, influencing their evolutionary dynamics and response to treatments.

Viral Structures

Most viruses are haploid, with the exception of the Retroviridae family, which contain two identical RNA molecules.
The primary difference between viruses and cells lies in their structural simplicity and reliance on host cells for replication.
Some viruses contain lipid envelopes, while others do not, contributing to their classification and infection strategies.

Viral Reproduction and Characteristics

Viruses reproduce through a series of steps that involve attachment, entry, replication, assembly, and release, differing fundamentally from cellular reproduction.
Essential organelles such as mitochondria and ribosomes are absent in viruses but are crucial for cellular function.

Intracellular Parasitism

Viruses are obligate intracellular parasites, meaning they require a host cell to replicate and thrive.
The genetic material in viruses can be either DNA or RNA, defining their classification and behavior in host organisms.

Antigenicity and Viral Components

Antigenicity refers to the ability of a virus to provoke an immune response in a host, which is vital for vaccine development.
Surface proteins, known as spikes, are crucial for viral attachment to specific receptors on host cells, facilitating infection.

Viral Recombination and Symmetry

Viral recombination involves the exchange of genetic material between different viral genomes, contributing to variation and adaptability.
Icosahedral symmetry features capsomers arranged in 20 triangular faces, providing structural integrity to viral particles.

Capsid and Viral Stability

The capsid is composed of protein subunits (capsomers) that protect the viral genome and aid in entry to host cells.
Enveloped viruses often have external surface proteins (spikes) that enhance infectivity and may affect overall virus stability.

Functional Roles of Viral Proteins

Outer surface proteins (spikes) facilitate viral attachment and entry into host cells, playing a critical role in infectivity.
Non-structural proteins perform various functions within the virus lifecycle, often involved in replication and host interaction.

Transmission and Envelope Influence

The transmission mode of enveloped viruses can be influenced by their lipid membrane, which affects stability and susceptibility to environmental factors.

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Description

Test your knowledge on viral taxonomy and classification. Explore topics such as viral nucleic acid type, symmetry of viral capsid, presence of lipid envelope, host range, mode of transmission, virus replication strategy, and the classification of viruses.