Questions and Answers
What is the primary function of the capsid in a virus?
What is a characteristic of viral genomes compared to cellular genomes?
What determines the specificity of a virus for a particular host cell?
What is the basis for viral classification?
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What do capsomeres refer to in a virus?
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What is a common characteristic of viral shapes?
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What is a characteristic of generalist viruses?
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What is the term for the combination of the capsid and genomic nucleic acids?
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Which of the following is a criterion for virus naming and classification?
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What is true about the type of nucleic acid in viral genomes?
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What is the term for a complete virus particle that includes a nucleic acid, a capsid, and in some cases an envelope?
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What is a common feature of viral hosts?
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What is the primary function of a virus?
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What is a characteristic of viruses?
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What is the result of a virus recruiting a cell's metabolic pathways?
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What is a consequence of viral infections?
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What is a characteristic of viruses in relation to their host cells?
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What is the meaning of the Greek word 'virus'?
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What is a characteristic of viruses in relation to their structure?
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What is the primary component of a virus?
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Study Notes
Virus Naming and Classification
- Virus names are usually based on the disease they are associated with, cyto-pathology they cause, site of isolation, places or people that discovered them, and biochemical features.
- Examples of virus names include HIV, Measles, Cytomegalovirus, Adenovirus, Enterovirus, Rhinovirus, RSV, Epstein-Barr virus, West Nile Fever, and Ebola.
Viral Taxonomy
- Viral classification is based on size and shape, whether they are enveloped or naked, nucleic acid composition, genome organization, and antigenic differences.
- Examples of classified viruses include Rotavirus and H1N1.
Virus Structure
- Capsomere is a protein subunit of the capsid.
- Capsid provides protection for viral nucleic acid and means of attachment to host cells.
- Capsid is composed of proteinaceous subunits called capsomeres.
- Capsomeres may be made of single or multiple types of proteins.
- Nucleocapsid is the capsid plus genomic nucleic acids (DNA or RNA).
Characteristics of Viruses
- Viruses show more variety in the nature of their genomes than cells.
- The primary way scientists categorize and classify viruses is based on their genetic material.
- Viral genomes can be DNA or RNA but never both.
- Viral genomes can be dsDNA, ssDNA, dsRNA, or ssRNA.
- Viral genomes can be linear and segmented or single and circular.
- Viral genomes are much smaller than genomes of cells.
Hosts of Viruses
- Most viruses infect only particular host cells due to the affinity of viral surface proteins for complementary proteins on host cell surface.
- Viruses can be specific to particular kinds of cells or hosts.
- Generalists infect many kinds of cells or many different hosts.
- All types of organisms are susceptible to some virus.
Viral Shapes
- Viruses can be classified by virion shape.
- Three basic types of viral shapes are helical, polyhedral (icosahedral), and complex.
- Examples of viral shapes include Tobacco mosaic virus (helical), polyhedral (common cold), and complex (Rabies virus and bacteriophage T4).
Definition of a Virus
- A virus is a package of genetic information protected by a protein shell for delivery into a host cell to be expressed and replicated.
- The term "virus" comes from the Greek word for "poison" and was initially described by Edward Jenner in 1798.
Characteristics of Viruses
- Viruses are minuscule, acellular, infectious agents having either DNA or RNA.
- Viruses cause infections of humans, animals, plants, and bacteria.
- Viruses cause most of the diseases that plague the industrialized world.
- Viruses cannot carry out any metabolic pathway, grow, respond to the environment, or reproduce independently.
- Viruses recruit the cell's metabolic pathways to increase their numbers.
- Viruses lack a cytoplasmic membrane, cytosol, or organelles.
- Viruses are obligate intracellular parasites.
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Description
This quiz covers the different ways viruses are named and classified, including by disease association, cyto-pathology, site of isolation, and discovery history.