what criteria are used in classification of viruses

What determines the classification and nomenclature of viruses?

Aside from physical data, genome structure and mode of replication are criteria applied in the classification and nomenclature of viruses, including the chemical composition and configuration of the nucleic acid, whether the genome is monopartite or multipartite.

What are the characteristics of a simple virus?

Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses may be viewed as mobile genetic elements, most probably of cellular origin and characterized by a long co-evolution of virus and host. For

What are the two types of viruses?

Accordingly, they are classified as DNA viruses and RNA viruses. The nucleic acid may be single or double stranded, circular or linear, segmented or unsegmented. As their name implies, DNA viruses use DNA as their genetic material.

What is Baltimore classification of viruses?

Baltimore classification (first defined in 1971) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid ( DNA or RNA ), strandedness (single-stranded or double-stranded), sense, and method of replication.

What 4 things are used to classify viruses?

Four characteristics were to be used for the classification of all viruses:Nature of the nucleic acid in the virion.Symmetry of the protein shell.Presence or absence of a lipid membrane.Dimensions of the virion and capsid.

What criteria are used to classify viruses quizlet?

Viruses are divided into families based on what criteria? size, structure, symmetry, type of genome, number of nucleic acid strands and their polarity, replication strategy. You just studied 80 terms!

What is are the most common methods used to identify viruses?

The most widely employed methods are viral culture and antigen detection by FA staining or EIA. Suitable specimens include nasopharyngeal aspirates, washings, or swabs; bronchial washings; and bronchoalveolar lavage fluid.

Do you think viruses should be classified as living organisms Why or why not?

Most biologists say no. Viruses are not made out of cells, they can't keep themselves in a stable state, they don't grow, and they can't make their own energy. Even though they definitely replicate and adapt to their environment, viruses are more like androids than real living organisms.

Are viruses classified bacteria?

On a biological level, the main difference is that bacteria are free-living cells that can live inside or outside a body, while viruses are a non-living collection of molecules that need a host to survive.

In which of the following ways do viruses differ from bacteria quizlet?

In which of the following ways do viruses differ from bacteria? Viruses are filterable. Viruses are obligate intracellular parasites. Viruses don't have any nucleic acid.

What term is used to specifically describe the types of viruses that infect bacteria?

A bacteriophage, or phage for short, is a virus that infects bacteria. Like other types of viruses, bacteriophages vary a lot in their shape and genetic material.

Which facts best support the position that viruses are not living organisms quizlet?

Which facts best support the position that viruses are not living organisms? Viruses are inert outside of a host and viruses cannot reproduce on their own. _________ phages have the option of entering the prophage state, while ___________ phages always burst the host cell shortly after infection.

What is the classification of a virus?

Classification of Virus on the Basis of Replication Properties and Site of Replication. All DNA viruses replicate and assemble in nucleus of host cell except Pox virus. All DNA virus, Retro virus and some tumor causing RNA virus replicates through ds DNA as intermediates.

Who developed the virus classification system?

The most commonly used system of virus classification was developed by Nobel Prize-winning biologist David Baltimore in the early 1970s.

How many copies of ssRNA are in Group VI?

Group VI viruses have diploid (two copies) ssRNA genomes that must be converted, using the enzyme reverse transcriptase, to dsDNA; the dsDNA is then transported to the nucleus of the host cell and inserted into the host genome. Then, mRNA can be produced by transcription of the viral DNA that was integrated into the host genome.

How many families of viruses are there?

The viruses that infect humans are currently grouped into 21 families, reflecting only a small part of the spectrum of the multitude of different viruses whose host ranges extend from vertebrates to protozoa and from plants and fungi to bacteria.

Which virus possesses RNA as genetic material?

The virus that possesses RNA as genetic material are called RNA viruses.

Which RNA tumor viruses contain both DNA and RNA?

The RNA tumor viruses called Leukoviruses and Rous’s viruses unusually contain both DNA and RNA as genetic material.

What are the different types of viruses?

Viruses range from the structurally simple and small parvoviruses and picornaviruses to the large and complex poxviruses and herpesviruses.

What is virus classification?

Jump to navigation Jump to search. Organisation of viruses into a taxonomic system. Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms . Viruses are classified by phenotypic ...

How are viruses classified?

Viruses are classified by phenotypic characteristics, such as morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause. The formal taxonomic classification of viruses is the responsibility of the International Committee on Taxonomy of Viruses (ICTV) system, although the Baltimore classification system ...

What are the three realms of viruses?

Viruses with a DNA genome, except for the DNA reverse transcribing viruses, are members of three of the four recognized viral realms: Duplodnaviria, Monodnaviria, and Varidnaviria. But the incertae sedis order Ligamenvirales, and many other incertae sedis families and genera, are also used to classify DNA viruses.

What is the Baltimore classification system?

Baltimore classification (first defined in 1971) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid ( DNA or RNA ), strandedness (single-stranded or double-stranded), sense , and method of replication. Named after David Baltimore, a Nobel Prize -winning biologist, these groups are designated by Roman numerals. Other classifications are determined by the disease caused by the virus or its morphology, neither of which are satisfactory due to different viruses either causing the same disease or looking very similar. In addition, viral structures are often difficult to determine under the microscope. Classifying viruses according to their genome means that those in a given category will all behave in a similar fashion, offering some indication of how to proceed with further research. Viruses can be placed in one of the seven following groups:

What is the ICTV?

The ICTV is the only body charged by the International Union of Microbiological Societies with the task of developing, refining, and maintaining a universal virus taxonomy. The system shares many features with the classification system of cellular organisms, such as taxon structure. However, some differences exist, ...

What is a virus species?

In 1991, the more specific principle that a virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche was adopted.

How are other classifications determined?

Other classifications are determined by the disease caused by the virus or its morphology, neither of which are satisfactory due to different viruses either causing the same disease or looking very similar . In addition, viral structures are often difficult to determine under the microscope.

What is the classification of viruses?

Virus classification is based mainly on characteristics of the viral particles, including the capsid shape, the type of nucleic acid (DNA or RNA, double stranded (ds) or single stranded (ss)) within the capsid, the process of replication, their host organisms, or the type of disease they cause.

What are viruses classified on?

Viruses can be classified on the basis of capsid shape, presence or absence of an envelope, and type of nucleic acid.

Is a virus a living organism?

This is largely due to the nature of viruses, which are not living organisms by the classic definition, but neither are they necessarily non-living. Therefore, viruses do not fit neatly into the biological classification system of cellular organisms, as plants and animals do.

What is the modern approach to virus classification based on?

Now that technologies for sequencing virus genomes and for determining genome organization are readily available, the modern approach to virus classification is based on comparisons of genome sequences and organizations. The degree of similarity between virus genomes can be assessed using computer programs, and can be represented in diagrams known as phylogenetic trees because they show the likely phylogeny (evolutionary development) of the viruses. Phylogenetic trees may be of various types ( Figure 10.1 ):

What are serotypes in a virus?

Serotypes reflect differences in virus proteins and have been found for many types of virus, including rotaviruses and foot and mouth disease virus.

What is ICTV in biology?

The ICTV lays down the rules for the nomenclature and classification of viruses, and it considers proposals for new taxonomic groups and virus names. Those that are approved are published in book form (please see Sources of further information at the end of this chapter) and on the web; these sources should be consulted for definitive information. The web site for this book ( www.wiley.com/go/carter) has links to relevant web sites.

Why are virologists useful?

Virologists are no different to other scientists in that they find it useful to classify the objects of their study into groups and subgroups. In the early days, when little was known about viruses, they were loosely grouped on the basis of criteria such as the type of host, the type of disease caused by infection, and whether the virus is transmitted by an arthropod vector.

Do viruses have taxonomic groups?

For a long time virologists were reluctant to use the taxonomic groups such as family, subfamily, genus, and species that have long been used to classify living organisms, but taxonomic groups of viruses have gradually been accepted and are now established ( Table 10.1 ). Some virus families have been grouped into orders, but higher taxonomic groupings, such as class and phylum, are not used. Only some virus families are divided into subfamilies.

What are the two major components of a virus?

The two major components of the virus used in classification are (1) the nucleic acid (its molecular weight and structure) and (2) the capsid (its size and symmetry and whether it is enveloped). A classification scheme based on these factors is presented in Tables 31–1 and 31–2 for DNA and RNA viruses, respectively.

What is the name of the virus that has a single stranded, linear, nonsegmented?

They have single-stranded, linear, nonsegmented, positive-polarity RNA. The main human pathogen is norovirus.

What is retrovirus?

The term retro pertain s to the reverse transcription of the RNA genome into DNA. There are two medically important groups: (1) the oncovirus group, which contains the sarcoma and leukemia viruses (e.g., human T-cell leukemia virus [HTLV]); and (2) the lentivirus (“slow virus”) group, which includes human immunodeficiency virus (HIV) and certain animal pathogens (e.g., visna virus). A third group, spumaviruses, is described in Chapter 46.

What type of virus is 100 nm?

They are noted for causing latent infections. The five important human pathogens are herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein–Barr virus (the cause of infectious mononucleosis).

What is the name of the virus that is a double stranded DNA?

Polyomaviruses. These are naked icosahedral viruses (45 nm in diameter) with double-stranded circular supercoiled DNA. Two human polyomaviruses are JC virus, isolated from patients with progressive multifocal leukoencephalopathy, and BK virus, isolated from the urine of immunosuppressed kidney transplant patients.

How many families of RNA viruses are there?

The 14 families of RNA viruses are described in Table 31–2. The three naked icosahedral virus families are listed first and are followed by the three enveloped icosahedral viruses. The remaining eight families are enveloped helical viruses; the first five have single-stranded linear RNA as their genome, whereas the last three have single-stranded circular RNA.

What is the smallest RNA virus?

These are the smallest (28 nm in diameter) RNA viruses. They have single-stranded, linear, nonsegmented, positive-polarity RNA within a naked icosahedral capsid. The name “picorna” is derived from pico (small), RNA -containing. There are two groups of human pathogens: (1) enteroviruses, such as poliovirus, Coxsackie virus, echovirus, and hepatitis A virus; and (2) rhinoviruses.

What is the name of the virus that is found in vertebrates?

parvovirinae (viruses of vertebrates) and densovirinae (viruses of insects)

How are enveloped virions released?

enveloped virions are released by budding, and non-enveloped virions by cell lysis.

Is parvoviridae linear or single stranded?

2. parvoviridae is single stranded but is (-) and linear

Overview

Definitions

Species form the basis for any biological classification system. Before 1982, it was thought that viruses could not be made to fit Ernst Mayr's reproductive concept of species, and so were not amenable to such treatment. In 1982, the ICTV started to define a species as "a cluster of strains" with unique identifying qualities. In 1991, the more specific principle that a virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecologi…

ICTV classification

Baltimore classification

Historical systems

Subviral agents

See also

Notes