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Endogenous Viral Element
An endogenous viral element (EVE) is a DNA sequence derived from a virus, and present within the germline of a non-viral organism. EVEs may be entire viral genomes ( proviruses), or fragments of viral genomes. They arise when a viral DNA sequence becomes integrated into the genome of a germ cell that goes on to produce a viable organism. The newly established EVE can be inherited from one generation to the next as an allele in the host species, and may even reach fixation. Endogenous retroviruses and other EVEs that occur as proviruses can potentially remain capable of producing infectious virus in their endogenous state. Replication of such 'active' endogenous viruses can lead to the proliferation of viral insertions in the germline. For most non-retroviral viruses, germline integration appears to be a rare, anomalous event, and the resulting EVEs are often only fragments of the parent virus genome. Such fragments are usually not capable of producing infectious virus, but may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. 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 16,000 of the millions of List of virus species, virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or ''virions'', consisting of (i) genetic material, i.e., long ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retrovirus
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a 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'' (backward). The new DNA is then retroviral integration, 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. Many retroviruses cause serious diseases in humans, other mammals, and birds. Retroviruses have many subfamilies in three basic groups. * Oncovirus, Oncoretroviruses (cancer-causing retroviruses) include human T-lymphotropic virus (HTLV) causing a type of leuk ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleocytoviricota
''Nucleocytoviricota'' is a phylum of viruses. Members of the phylum are also known as the nucleocytoplasmic large DNA viruses (NCLDV), which serves as the basis of the name of the phylum with the suffix - for virus phylum. These viruses are referred to as nucleocytoplasmic because they are often able to replicate in both the host's cell nucleus and cytoplasm. The phylum is notable for containing the giant viruses. There are nine families of NCLDVs that all share certain genomic and structural characteristics; however, it is uncertain whether the similarities of the different families of this group have a common viral ancestor. One feature of this group is a large genome and the presence of many genes involved in DNA repair, DNA replication, transcription, and translation. Typically, viruses with smaller genomes do not contain genes for these processes. Most of the viruses in this family also replicate in both the host's nucleus and cytoplasm, thus the name nucleocytoplasmic. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about eight phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta. General description The term phylum was coined in 1866 by Ernst Haeckel from the Greek (, "race, stock"), related to (, "tribe, clan"). Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguishe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant Virus
A giant virus, sometimes referred to as a girus, is a very large virus, some of which are larger than typical bacteria. All known giant viruses belong to the phylum ''Nucleocytoviricota''. Description While the exact criteria as defined in the scientific literature vary, giant viruses are generally described as viruses having large, pseudo-Capsid#Icosahedral, icosahedral capsids (200 to 400 nanometers in diameter) that may be surrounded by a thick (approximately 100 nm) layer of filamentous protein fibers. The viruses have large, double-stranded DNA genomes (300 to >1000 kilobasepairs) that encode a large contingent of genes (of the order of 1000 genes). The best characterized giant viruses are the phylogenetically related mimivirus and megavirus, which belong to the family ''Mimiviridae'' (aka ''Megaviridae''), and are distinguished by their large capsid diameters. Giant viruses from the deep ocean, terrestrial sources, and human patients contain genes encoding Cytochrome P4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geminiviridae
''Geminiviridae'' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. The family contains 15 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 (i.e. geminivirus genomes are ambisense). According to the Baltimore classification they are considered class II viruses. It is the largest known family of single stranded DNA viruses. Mastrevirus and curtovirus Transmission (medicine), transmission is via various leafhopper species (e.g. maize streak virus and other African streak viruses are transmitted by ''Cicadulina mbila''), the only known topocuvirus species, ''Tomato pseudo-curly top virus'', is transmitted by the treehopper ''Micrutalis malleifera'', and begomoviruses are trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cauliflower Mosaic Virus
Cauliflower mosaic virus (CaMV) is a member of the genus ''Caulimovirus'', one of the six genera in the family ''Caulimoviridae'', which are pararetroviruses that infect plants. Pararetroviruses replicate through reverse transcription just like retroviruses, but the viral particles contain DNA instead of RNA. Definition The cauliflower mosaic virus (CaMV) is a member of the family ''Caulimoviridae''. This family is grouped together with the ''Belpaoviridae'', ''Metaviridae'', ''Pseudoviridae'', and ''Retroviridae'' (all of which instead have an RNA genome replicated via a DNA intermediate) in the order ''Ortervirales''; the ''Hepadnaviridae'', despite having a DNA genome replicated via an RNA intermediate (like the ''Caulimoviridae''), are more distantly related, belonging to the separate order ''Blubervirales'' (both orders belong to the same class, the '' Revtraviricetes''). CaMV infects mostly plants of the family Brassicaceae (such as cauliflower and turnip) but some CaM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circoviridae
''Circoviridae'' is a family of DNA viruses. Birds and mammals serve as natural hosts. The family has two genera. Diseases associated with this family include: PCV-2: postweaning multisystemic wasting syndrome; CAV: chicken infectious anemia. Structure Viruses in the family ''Circoviridae'' are non-enveloped, with icosahedral and round geometries, and T=1 symmetry. The diameter is around 20 nm. Genomes are circular and non-segmented, around 3.8kb in length. The capsid consists of 12 pentagonal trumpet-shaped pentamers. There are two main open reading frames arranged in opposite directions that encode the replication and capsid proteins. Life cycle Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. Replication follows the ssDNA rolling circle model. DNA templated transcription, with some alternative splicing mechanism is the method of transcription. The virus exits the host cell by nuclear egress, and nuclear pore expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bornavirus
''Bornaviridae'' is a family of negative-strand RNA viruses in the order ''Mononegavirales''. Horses, sheep, cattle, rodents, birds, reptiles, and humans serve as natural hosts. Diseases associated with bornaviruses include Borna disease, a fatal neurologic disease of mammals restricted to central Europe; and Proventricular dilatation disease, proventricular dilatation disease (PDD) in birds. Bornaviruses may cause encephalitis in mammals like horses or sheep. The family contains four genera. History Borna disease was first identified in 1926 and its genome was isolated in 1990. The ICTV proposed the creation in 1996 of the family ''Bornaviridae'' along with the genus ''Bornaviru''s (today ''Orthobornavirus''). The viral family is named after the city of Borna, Leipzig, Borna in Saxony, Saxony, Germany, which is where many animals were lost to the sporadic encephalopathy caused by the viral disease. Structure Orthobornavirions are enveloped, with spherical geometries and he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filoviridae
''Filoviridae'' () is a International Committee on Taxonomy of Viruses, family of RNA virus#Group_V_–_negative-sense_ssRNA_viruses, single-stranded negative-sense RNA viruses in the order (biology), order ''Mononegavirales''. Two members of the family that are commonly known are Zaire ebolavirus, Ebola virus and Marburg virus. Both viruses, and some of their lesser known relatives, cause severe disease in humans and nonhuman primates in the form of viral hemorrhagic fevers. All filoviruses are classified by the US as select agents, by the World Health Organization as Risk Group 4 Pathogens (requiring Biosafety, Biosafety Level 4-equivalent containment), by the National Institutes of Health/National Institute of Allergy and Infectious Diseases as Category A Priority Pathogens, and by the Centers for Disease Control and Prevention as Bioterrorism, Category A Bioterrorism Agents, and are listed as Biological Agents for Export Control by the Australia Group. Use of term The Interna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parvoviridae
Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the protein the viral capsid is made of. The coding portion of the genome is flanked by telomeres at each end that form into Stem-loop, hairpin loops that are important during replication. Parvovirus virions are small compared to most viruses, at 23–28 nanometers in diameter, and contain the genome enclosed in an icosahedral capsid that has a rugged surface. Parvoviruses enter a host cell by endocytosis, travelling to the nucleus where they wait until the cell enters its replication stage. At that point, the genome is uncoated and the coding portion is replicated. Viral messenger RNA (mRNA) is then Transcription (biology), transcribed and Translation (biology), translated, resulting in NS1 initiating replication. During replication, the hairpi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Replication
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. Viral production / replication Viruses multiply only in living cells. The host cell must provide the energy and synthetic machinery and the low-molecular-weight precursors for the synthesis of viral proteins and nucleic acids. Virus replication occurs in seven stages: # Attachment # Entry (penetration) # Uncoating # Replication # Assembly # Maturation # Release (liberation stage). Attachment It is the first step of viral replication. Some viruses attach to the cell membrane of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
