Virus Classification Flashcards

Questions and Answers

Why classify viruses?

To compare viruses and to analyze and understand virus structure, replication pathways, interactions with host cells, and disease transmission.

What is the ranking of viruses?

Order, Families, Genus, Species

How are viruses molecularly classified?

By type of nucleic acid (DNA or RNA), strandedness of nucleic acid (ss or ds), topology (circular or linear), symmetry of capsid (icosahedral, helical or no symmetry), and presence or absence of envelope.

How can viruses be genetically related to one another?

Through their genome sequences, their amino acid sequences of viral proteins, their order of genes on viral genome, the mechanism of viral mRNA synthesis they use, the presence of viral genes for coding DNA or RNA polymerases, the use of RT during replication. Signup and view all the answers

What are some viral adaptations?

Mechanism of transmission, entry pathway into cells, and interaction with cellular pathway. Signup and view all the answers

How has virus entry into cells adapted?

Through binding of specific cell surface receptors, passage through cell walls in plants, entry by membrane fusion, and uptake via vesicles. Signup and view all the answers

How have the mechanisms of viral transmission adapted?

Direct contact via body fluids, respiratory droplets, stool or urine contamination, and insect vectors. Signup and view all the answers

How has the interaction with cellular proteins in viruses adapted?

Through RNA or DNA polymerase, host or viral RNA processing enzymes, and protein synthesizing systems. Signup and view all the answers

What are segmented genes?

Genes that can make a protein per gene segmented. Signup and view all the answers

What kind of viruses tend to infect organisms with only one category?

Viruses that are evolutionary and genetically related, such as those infecting bacteria, archaea, lower eukaryotes, plants, invertebrates, and vertebrates. Signup and view all the answers

Is it always the case that viruses only infect organisms within one organism?

False Signup and view all the answers

What does the ability of viruses to infect more than one type of organism show us?

It shows us that viruses can evolve and spread in both vertebrates/plants and invertebrates. Signup and view all the answers

What is the International Committee of Taxonomy of Viruses (ICTV) and what are their objectives?

The naming committee of viruses aimed to develop internationally agreed taxonomy for viruses, communicate decisions to the international virology community, and maintain names of virus taxa. Signup and view all the answers

Describe characteristics of viruses that are in the same family.

They usually share overall genome organization, virion structure, and replication mechanisms, but vary in virion size, genome length, and may have unique genes. Signup and view all the answers

Describe characteristics of viruses that are in the same genus.

They usually share genome organization and size, virion structure, and replication strategies, but can diverge significantly in sequences. Signup and view all the answers

Describe the characteristics of viruses that are in the same species.

They exhibit a high degree of similarity between nucleic acid and amino acid sequences, infect limited organisms or specific target cells, and share a common lineage. Signup and view all the answers

What are the suffixes of virus orders, families, and genera?

-Virales, -viridae, and -virus Signup and view all the answers

Historically, research on viruses has been carried out by scientists studying viruses that infect...

This statement remains incomplete. It may relate to specific organisms or types of viruses, which research historically focused on. Signup and view all the answers

Study Notes

Virus Classification Overview

Classification aids in understanding virus structure, replication, host interactions, and disease transmission.
Virus taxonomy ranks include Order, Families, Genus, and Species.

Molecular Classification

Viruses are classified based on nucleic acid type (DNA/RNA), strandedness (ss/ds), topology (circular/linear), capsid symmetry (icosahedral/helical/no symmetry), and presence of an envelope.

Genetic Relationships

Viruses are genetically related through their genome sequences, amino acid sequences of viral proteins, gene order on genomes, mechanisms of viral mRNA synthesis, and presence of polymerase coding genes.

Viral Adaptations

Adaptations in viruses include mechanisms of transmission, entry pathways into host cells, and interactions with cellular pathways.

Virus Entry Mechanisms

Adaptations for cell entry include binding to specific receptors, passage through cell walls in plants, membrane fusion, and uptake via vesicles.

Mechanisms of Transmission

Modes of viral transmission consist of direct contact (e.g., HIV), respiratory droplets (e.g., Influenza), fecal contamination (e.g., Rotavirus), and insect vectors (e.g., Zika).

Interaction with Cellular Proteins

Viruses adapt by utilizing RNA or DNA polymerases, host/viral RNA processing enzymes, and protein synthesis systems.

Segmented Genes

Segmented genes refer to genes segmented in a way that each can produce its own protein.

Viruses and Host Organisms

Viruses often exhibit specificity for one organism category, affecting bacteria, archaea, lower eukaryotes, plants, and invertebrates.

Cross-Species Infection

Some viruses can infect multiple organism types, evidenced by vertebrate viruses transmitting via blood-sucking invertebrates (e.g., mosquitoes).

Evolutionary Implications

Multi-host infection capability illustrates viral evolution and adaptability across vertebrates and plants.

ICTV (International Committee of Taxonomy of Viruses)

The ICTV is responsible for developing standardized virus taxonomy and names, communicating decisions to virologists, and maintaining virus nomenclature.

Characteristics of Viral Families

Viruses in the same family typically exhibit similar genome organization, virion structure, and replication mechanisms but can differ in size, genome length, and unique genes.

Characteristics of Viral Genera

Viruses within a genus share genome organization, size, and replication strategies but can show substantial sequence divergence and can infect different hosts or tissues.

Characteristics of Viral Species

Viruses classified as the same species feature high nucleic acid and amino acid similarity, targeting specific organisms or tissues, and common lineage due to close genetic relationships.

Taxonomy Suffixes

Virus orders end with "-virales," families with "-viridae," and genera with "-virus."

Historical Research Focus

Historically, virus research has largely centered on viruses that infect a range of organisms.

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Description

Explore the essential aspects of virus classification with these flashcards. This quiz covers virus structure, replication pathways, and molecular classification methods. Perfect for anyone studying virology or microbiology.