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Retroviruses
Virus classification
Group: Group VI (ssRNA-RT)
Family: Retroviridae
Genera

Subfamily: Orthoretrovirinae

Alpharetrovirus
Betaretrovirus
Gammaretrovirus
Deltaretrovirus
Epsilonretrovirus
Lentivirus

Subfamily: Spumaretrovirinae

Spumavirus

A retrovirus is any virus belonging to the viral family Retroviridae. Virus classification involves naming and placing Viruses into a taxonomic system A reverse transcribing virus is any virus which replicates using Reverse transcription, the formation of DNA from an RNA template An alpharetrovirus is a Genus of the Retroviridae family. It has type C morphology. A betaretrovirus is a Genus of the Retroviridae family. It has type B or type C morphology. A gammaretrovirus is a Genus of the Retroviridae family. Many species contain Oncogenes and cause Sarcomas and Leukemias A deltaretrovirus is a Genus of the Retroviridae family. It consists of Exogenous horizontally-transmitted viruses found in several groups of An epsilonretrovirus is a Genus of the Retroviridae family. It infects Fish. Lentivirus ( lenti-, Latin for " slow " is a Genus of slow Viruses of the Retroviridae family A spumavirus or foamyvirus is a Genus of the Retroviridae family. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable They are enveloped viruses possessing an RNA genome, and replicate via a DNA intermediate. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Retroviruses rely on the enzyme reverse transcriptase to perform the reverse transcription of its genome from RNA into DNA, which can then be integrated into the host's genome with an integrase enzyme. In Biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase Enzyme that transcribes Transcription is the synthesis of RNA under the direction of DNA The pre-integration complex is generally composed of the viral genetic material and associated proteins (viral and host after release into the cell Integrase is an enzyme produced by a Retrovirus (including HIV) that enables its genetic material to be integrated into the DNA of the infected cell The virus then replicates as part of the cell's DNA.

Contents

Description of virus

The virus itself stores its nucleic acid, in the form of a +mRNA (including the 5'cap and 3'PolyA inside the virion) genome and serves as a means of delivery of that genome into cells it targets as an obligate parasite, and constitutes the infection. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called An obligate parasite is a parasitic Organism that cannot live independently of its host. An infection is the detrimental Colonization of a host Organism by a foreign Species. Once in the host's cell, the RNA strands undergo reverse transcription in the cytosol and are integrated into the host's genome, at which point the retroviral DNA is referred to as a provirus. Reverse transcription is the process of making a double stranded DNA (deoxyribonucleic acid molecule from a single stranded RNA (ribonucleic acid template The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. A provirus is a Virus genome that has integrated itself into the DNA of a host cell.

Multiplication

When retroviruses have integrated their own genome into the germ line, their genome is passed on to a following generation. In Biology and Genetics, the germline of a mature or developing individual is the line (sequence of Germ cells that have genetic material that "Heir" and "Heiress" redirect here For the men and women fragrances endorsed by Paris Hilton see Heiress (fragrance. These endogenous retroviruses, contrasted with exogenous ones, now make up 5-8% of the human genome. Endogenous retroviruses are Retroviruses derived from ancient infections of Germ cells in Humans Mammals and other vertebrates as such their Exogenous DNA refers to any deoxyribonucleic acid that originates outside of the organism of concern or study [1] Most insertions have no known function and are often referred to as "junk DNA". In Molecular biology, junk DNA is a provisional label for the portions of the DNA sequence of a Chromosome or a Genome for which no However, many endogenous retroviruses play important roles in host biology, such as control of gene transcription, cell fusion during placental development in the course of the germination of an embryo, and resistance to exogenous retroviral infection. The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation Germination is the process whereby growth emerges from a period of dormancy An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular Endogenous retroviruses have also received special attention in the research of immunology-related pathologies, such as autoimmune diseases like multiple sclerosis, although endogenous retroviruses have not yet been proven to play any causal role in this class of disease. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with Autoimmune diseases arise from an overactive Immune response of the body against substances and tissues normally present in the body Multiple sclerosis (abbreviated MS also known as disseminated sclerosis or encephalomyelitis disseminata) is an autoimmune condition in which the The role of endogenous retroviruses in human gene evolution is explored in a 2005 peer-reviewed article. [2]

While transcription was classically thought to only occur from DNA to RNA, reverse transcriptase transcribes RNA into DNA. In Biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase Enzyme that transcribes The term "retro" in retrovirus refers to this reversal (making DNA from RNA) of the central dogma of molecular biology. The central dogma of molecular biology was first enunciated by Francis Crick in 1958 and re-stated in a Nature paper published in 1970 Reverse transcriptase activity outside of retroviruses has been found in almost all eukaryotes, enabling the generation and insertion of new copies of retrotransposons into the host genome. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Retrotransposons (also called transposons via RNA intermediates are genetic elements that can amplify themselves in a Genome and are ubiquitous components of the It is important to note that a retrovirus must "bring" its own reverse transcriptase in its capsid, otherwise it is unable to utilize the infected cell's enzymes to carry out the task, due to the unusual nature of producing DNA from RNA. For the leaf bug see Miridae. A capsid is the protein shell of a virus.

Because reverse transcription lacks the usual proofreading of DNA replication, this kind of virus mutates very often. Proofreading traditionally means reading a proof copy of a text in order to detect and correct any errors In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism This enables the virus to grow resistant to antiviral pharmaceuticals quickly, and impedes the development of effective vaccines and inhibitors for the retrovirus. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with A vaccine is a biological preparation which is used to establish or improve immunity to a particular disease [3]

Genes

Retrovirus genomes commonly contain these three open reading frames that encode for proteins that can be found in the mature virus:


Provirus

This DNA can be incoporated into host genome as a provirus that can be passed on to progeny cells. In this way some retroviruses can convert normal cells into cancer cells.

Development of retroviruses

Studies of retroviruses led to the first demonstrated synthesis of DNA from RNA templates, a fundamental mode for transferring genetic material that occurs in both eukaryotes and prokaryotes. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other

It has been speculated that the RNA to DNA transcription processes used by retroviruses may have first caused DNA to be used as genetic material.

In this model, the RNA world hypothesis, cellular organisms adopted the more chemically stable DNA when retroviruses evolved to create DNA from the RNA templates. The RNA world hypothesis proposes that a world filled with life based on Ribonucleic acid (RNA predated current life based on Deoxyribonucleic acid (DNA Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units

Classification

Exogenous

The following genera are included here:

These were previously divided into three subfamilies (Oncovirinae, Lentivirinae, and Spumavirinae), but with current knowledge of retroviruses, this is no longer appropriate. An alpharetrovirus is a Genus of the Retroviridae family. It has type C morphology. Avian leukosis virus is a Species of Retrovirus that causes disease in Chickens experimentally it can infect other species of birds and mammals A betaretrovirus is a Genus of the Retroviridae family. It has type B or type C morphology. Mouse mammary tumor virus (MMTV is a milk transmitted Retrovirus like the HTL viruses HI viruses and BLV. A gammaretrovirus is a Genus of the Retroviridae family. Many species contain Oncogenes and cause Sarcomas and Leukemias The murine leukemia virus belongs to the gammaretroviral genus of the Retroviridae family of Viruses their hosts are Vertebrates. Feline leukemia virus ( FeLV) is a Retrovirus that infects Cats As a retrovirus the genetic information of FeLV is carried by RNA instead A deltaretrovirus is a Genus of the Retroviridae family. It consists of Exogenous horizontally-transmitted viruses found in several groups of Bovine leukemia virus ( BLV) is a bovine virus closely related to HTLV-I, a Human tumour virus. Human T-lymphotropic virus (HTLV is a Human, single-stranded RNA Retrovirus that causes T-cell Leukemia and T-cell Lymphoma An epsilonretrovirus is a Genus of the Retroviridae family. It infects Fish. Lentivirus ( lenti-, Latin for " slow " is a Genus of slow Viruses of the Retroviridae family Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome Simian immunodeficiency virus ( SIV) is a Retrovirus that is found in numerous strains in Primates; the specific strains infecting Humans Feline immunodeficiency virus ( FIV) occasionally referred to as Feline or Cat AIDS is a Lentivirus that affects domesticated A spumavirus or foamyvirus is a Genus of the Retroviridae family. (The term oncovirus is still commonly used, though. An oncovirus is a Virus associated with Cancer. Oncoviruses come in two different forms viruses with a DNA Genome, such as Adenovirus )

Endogenous

Main article: endogenous retrovirus

Endogenous retroviruses are not formally included in this classification system, and are broadly classified into three classes, on the basis of relatedness to exogenous genera:

Treatment

Main article: Antiretroviral drug

Antiretroviral drugs are medications for the treatment of infection by retroviruses, primarily HIV. Endogenous retroviruses are Retroviruses derived from ancient infections of Germ cells in Humans Mammals and other vertebrates as such their Different classes of antiretroviral drugs act at different stages of the HIV life cycle. Combination of several (typically three or four) antiretroviral drugs is known as highly active anti-retroviral therapy (HAART).

Genetic barrier

The genetic barrier is loosely defined as the difficulty for retroviruses to evade antiretroviral drugs by mutating into resistant types. [4]

References

  1. ^ Robert Belshaw; Pereira V; Katzourakis A; Talbot G; Paces J; Burt A; Tristem M. (April 2004). "Long-term reinfection of the human genome by endogenous retroviruses". Proc Natl Acad Sci U S A 101 (14): 4894–99. PMID 15044706.  
  2. ^ Medstrand P, van de Lagemaat L, Dunn C, Landry J, Svenback D, Mager D (2005). "Impact of transposable elements on the evolution of mammalian gene regulation". Cytogenet Genome Res 110 (1-4): 342-52. doi:10.1159/000084966. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16093686.  
  3. ^ Svarovskaia ES; Cheslock SR; Zhang WH; Hu WS; Pathak VK. (Jan 2003). "Retroviral mutation rates and reverse transcriptase fidelity.". Front Biosci. : 117-134.  
  4. ^ Computing the genetic barrier N. Beerenwinkel, T. Sing, M. Daumer, R. Kaiser, T. Lengauer.

External links


Viruses templates

Dictionary

retrovirus

-noun

  1. (virology) A virus that has a genome consisting of RNA.
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