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A retrovirus is a type of virus that inserts a copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus.
Virology is the study of viruses – submicroscopic, parasitic particles of genetic material contained in a protein coat – and virus-like agents. It focuses on the following aspects of viruses: their structure, classification and evolution, their ways to infect and exploit host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy. Virology is a subfield of microbiology.
Reoviridae is a family of viruses. They have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their genomes of discrete double-stranded segments of RNA within multi-layered capsids. Lack of a lipid envelope has allowed three-dimensional structures of these large complex viruses to be obtained, revealing a structural and likely evolutionary relationship to the Cystovirus family of Bacteriophage. There are currently 97 species in this family, divided among 15 genera in two subfamilies. Reoviruses can affect the gastrointestinal system and respiratory tract. The name "Reo-" is derived from respiratory entericorphan viruses. The term "orphan virus" refers to the fact that some of these viruses have been observed not associated with any known disease. Even though viruses in the family Reoviridae have more recently been identified with various diseases, the original name is still used.
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA, and it is DNase resistant. Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome.
The hepatitis E virus (HEV) is the causative agent of hepatitis E. It is of the species Orthohepevirus A.
Reassortment is the mixing of the genetic material of a species into new combinations in different individuals. Several different processes contribute to reassortment, including assortment of chromosomes, and chromosomal crossover. It is particularly used when two similar viruses that are infecting the same cell exchange genetic material. In particular, reassortment occurs among influenza viruses, whose genomes consist of eight distinct segments of RNA. These segments act like mini-chromosomes, and each time a flu virus is assembled, it requires one copy of each segment.
Non-Mendelian inheritance is any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the genotypes of both parents in a genetic cross are known, Mendel's laws can be used to determine the distribution of phenotypes expected for the population of offspring. There are several situations in which the proportions of phenotypes observed in the progeny do not match the predicted values.
Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants.
Geminiviridae is a family of plant viruses. There are currently 485 species in this family, divided among 9 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosaic, yellow mottle, leaf curling, stunting, streaks, reduced yields. They have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication. According to the Baltimore classification they are considered class II viruses. It is the largest known family of single stranded DNA viruses.
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm.
The genus Orbivirus is a member of the Reoviridae family, in the subfamily Sedoreovirinae. Unlike the other reoviruses, orbiviruses are arboviruses. This genus currently contains 22 species and at least 130 different serotypes. Orbiviruses can infect and replicate within a wide range of arthropod and vertebrate hosts. Orbiviruses are named after their characteristic doughnut-shaped capsomers.
Herpes simplex virus1 and 2, also known by their taxonomical names Human alphaherpesvirus 1 and Human alphaherpesvirus 2, are two members of the human Herpesviridae family, a set of new viruses that produce viral infections in the majority of humans. Both HSV-1 and HSV-2 are common and contagious. They can be spread when an infected person begins shedding the virus.
The Simian foamy virus (SFV) is a species of the genus Spumavirus, which belongs to the family of Retroviridae. It has been identified in a wide variety of primates, including pro-simians, New World and Old World monkeys as well as apes, and each species has been shown to harbor a unique (species-specific) strain of SFV, including African green monkeys, baboons, macaques and chimpanzees. As it is related to the more well-known retrovirus human immunodeficiency virus (HIV), its discovery in primates has led to some speculation that HIV may have been spread to the human species in Africa through contact with blood from apes, monkeys, and other primates, most likely through bushmeat hunting practices.
The main idea behind viral processing is to stop the viruses in a given sample from contaminating the desired product. The two most widely used methods of viral processing are viral removal and viral inactivation. The former is a method in which all viruses are simply removed from the sample completely. The latter method is one in which the viruses may remain in the final product, but in a non-infective form. These techniques are used widely in the food and blood plasma industries, as those products can be harmed by the presence of viral particles. Some of the more common viruses removed by these methods are the HIV-1 and HIV-2 viruses; hepatitis A, B, and C; and parvoviruses. The methods used in the plasma industry have been summarized In some cases, however, it is the virus itself that is the desired product, as is often the case with the HIV. In many cases, researchers may be trying to extract the viruses from the blood for study, not specifically for blood purification. It is also common to use these types of techniques to remove particles produced as a result of viral infection.
Cucumber mosaic virus (CMV) is a plant pathogenic virus in the family Bromoviridae. It is the type member of the plant virus genus, Cucumovirus. This virus has a worldwide distribution and a very wide host range. In fact it has the reputation of having the widest host range of any known plant virus. It can be transmitted from plant to plant both mechanically by sap and by aphids in a stylet-borne fashion. It can also be transmitted in seeds and by the parasitic weeds, Cuscuta sp. (dodder).
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants, and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 6,000 virus species have been described in detail, of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology.
The transmission of hepadnaviruses between their natural hosts, humans, non-human primates, and birds, including intra-species host transmission and cross-species transmission, is a topic of study in virology.
Gene therapy utilizes the delivery of DNA into cells, which can be accomplished by several methods, summarized below. The two major classes of methods are those that use recombinant viruses and those that use naked DNA or DNA complexes.
This glossary of virology is a list of definitions of terms and concepts used in the study of virology, particularly in the description of viruses and their actions. Related fields include microbiology, molecular biology, and genetics.
Bovine foamy virus (BFV) is a ss(+)RNA retrovirus that belongs to the genus spumaviridae. Spumaviruses are differ from the other six members of family retroviridae, both structurally and in pathogenic nature. Supma viruses derive their name from spuma the latin for "foam". The 'foam' part of 'foamy virus' comes from syncytium formation and the rapid vacuolization of infected cells which creates a 'foamy' appearance.
References
- ↑ "Viral Genetics" . Retrieved 2009-04-06.
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