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Baltimore Classification
Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a distinct group. Seven Baltimore groups are described that take into consideration whether the viral genome is made of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), whether the genome is single- or double-stranded, and whether the sense of a single-stranded RNA genome is positive or negative. Baltimore classification also closely corresponds to the manner of replicating the genome, so Baltimore classification is useful for grouping viruses together for both transcription and replication. Certain subjects pertaining to viruses are associated with multiple, specific Baltimore groups, such as specific forms of translation of mRNA and the host range of different types of viruses. Structural characteristics such as the shape of the viral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus Classification
Virus classification is the process of naming viruses and placing them into a taxonomy (biology), taxonomic system similar to the classification systems used for cell (biology), cellular organisms. Viruses are classified by phenotypic characteristics, such as Virus#Structure, morphology, nucleic acid type, mode of replication, Host (biology), 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 can be used to place viruses into one of seven groups based on their manner of mRNA synthesis. Specific naming conventions and further classification guidelines are set out by the ICTV. In 2021, the ICTV changed the International Code of Virus Classification and Nomenclature (ICVCN) to mandate a binomial format (genus, , , , species) for naming new viral species similar to that used for cellular organisms; the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adnaviria
''Adnaviria'' is a Realm (virology), realm of viruses that includes archaeal viruses that have a filamentous virion (i.e. body) and a linear, double-stranded DNA genome. The genome exists in A-form (A-DNA) and encodes a dimeric major capsid protein (MCP) that contains the SIRV2 fold, a type of alpha-helix bundle containing four helices. The virion consists of the genome encased in capsid proteins to form a helical nucleoprotein complex. For some adnaviruses, this helix is surrounded by a lipid membrane called an Viral envelope, envelope. Some contain an additional protein layer between the nucleoprotein helix and the envelope. Complete virions are long and thin and may be flexible or a stiff like a rod. ''Adnaviria'' was established in 2020 after cryogenic electron microscopy showed that the viruses in the realm were related due to a shared MCP, A-DNA, and general virion structure. Viruses in ''Adnaviria'' infect hyperthermophilic and acidophilic archaea, i.e. archaea that inhabit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Papillomavirus
''Papillomaviridae'' is a family of non- enveloped double-stranded DNA viruses whose members are known as papillomaviruses. Several hundred species of papillomaviruses, traditionally referred to as "types", have been identified infecting all carefully inspected mammals, but also other vertebrates such as birds, snakes, turtles and fish. Infection by most papillomavirus types, depending on the type, is either asymptomatic (e.g. most Beta-PVs) or causes small benign tumors, known as papillomas or warts (e.g. human papillomavirus 1, HPV6 or HPV11). Papillomas caused by some types, however, such as human papillomaviruses 16 and 18, carry a risk of becoming cancerous. Papillomaviruses are usually considered as highly host- and tissue- tropic, and are thought to rarely be transmitted between species. Papillomaviruses replicate exclusively in the basal layer of the body surface tissues. All known papillomavirus types infect a particular body surface, typically the skin or mucosal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Papovaviricetes
''Papovaviricetes'' is a class of viruses. The class shares the name of an abolished family, ''Papovaviridae'', which was split in 1999 into the two families ''Papillomaviridae'' and ''Polyomaviridae''. The class was established in 2019 and takes its name from the former family. Orders The following orders are recognized: * ''Sepolyvirales'' * ''Zurhausenvirales'' See also * Bandicoot papillomatosis carcinomatosis virus Bandicoot papillomatosis carcinomatosis viruses are a pair of circular double-stranded DNA virus isolated from bandicoots ('' Perameles bougainville''). The genomes have features similar to viruses in the families ''Papillomaviridae'' and the '' ... References Viruses {{Virus-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herpesvirales
''Herpesvirales'' is an order of dsDNA viruses (Baltimore group I) with animal hosts, characterised by a common morphology consisting of an icosahedral capsid enclosed in a glycoprotein-containing lipid envelope. Common infections in humans caused by members of this order include cold sores, genital herpes, chickenpox, shingles, and glandular fever. ''Herpesvirales'' is the sole order in the class ''Herviviricetes'', which is the sole class in the phylum ''Peploviricota''. Virology Morphology All members of the order have a virion structure that consists of a DNA core surrounded by an icosahedral capsid composed of 12 pentavalent and 150 hexavalent capsomeres (T = 16). The capsid has a diameter of ~110 nanometers (nm) and is embedded in a proteinaceous matrix called the tegument, which in its turn is enclosed by a glycoprotein-containing lipid envelope with a diameter of about 200 nm. The DNA genome is linear and double stranded, with sizes in the range 125–290 kbp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caudoviricetes
''Caudoviricetes'' is a class of viruses known as tailed viruses and head-tail viruses (''cauda'' is Latin for "tail"). It is the sole representative of its own phylum, ''Uroviricota'' (from ''ouros'' (ουρος), a Greek word for "tailed" + -viricota). Under the Baltimore classification scheme, the ''Caudoviricetes'' are group I viruses as they have double stranded DNA (dsDNA) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape; each virion has an icosahedral head that contains the viral genome, and is attached to a flexible tail by a connector protein. The order encompasses a wide range of viruses, many containing genes of similar nucleotide sequence and function. However, some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, even among the same genus. Due to their characteristic structure and possession of potentially homologous genes, it is believed these viruse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even though the domain Archaea Cladistics, cladistically includes eukaryotes, the term "archaea" (: archaeon , from the Greek "ἀρχαῖον", which means ancient) in English still generally refers specifically to prokaryotic members of Archaea. Archaea were initially Taxonomy (biology), classified as bacteria, receiving the name archaebacteria (, in the Archaebacteria Kingdom (biology), kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from Bacteria and Eukaryote, Eukaryota. Archaea are further divided into multiple recognized phylum, phyla. Classification is difficult because most have not been Isolation (microbiology), isolated in a laboratory and have been detected only by their Gene, gene s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Replicative Transposition
Replicative transposition is a mechanism of transposition in molecular biology, proposed by James A. Shapiro in 1979, in which the transposable element is duplicated during the reaction, so that the transposing entity is a copy of the original element. In this mechanism, the donor and receptor DNA sequences form a characteristic intermediate "theta" configuration, sometimes called a "Shapiro intermediate". Replicative transposition is characteristic to retrotransposon Retrotransposons (also called Class I transposable elements) are mobile elements which move in the host genome by converting their transcribed RNA into DNA through reverse transcription. Thus, they differ from Class II transposable elements, or ...s and occurs from time to time in class II transposons.. References {{DEFAULTSORT:Replicative Transposition Mobile genetic elements ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyadenylation
Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression. The process of polyadenylation begins as the transcription of a gene terminates. The 3′-most segment of the newly made pre-mRNA is first cleaved off by a set of proteins; these proteins then synthesize the poly(A) tail at the RNA's 3′ end. In some genes these proteins add a poly(A) tail at one of several possible sites. Therefore, polyadenylation can produce more than one transcript from a single gene (alternative polyadenylation), similar to alternative splicing. The poly(A) tail is important for the nuclea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA, a process called transcription. A transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region before RNAP can initiate the DNA unwinding at that position. RNAP not only initiates RNA transcription, it also guides the nucleotides into position, facilitates attachment and elongation, has intrinsic proofreading and replacement capabilities, and termination recognition capability. In eukaryotes, RNAP can build chains as long as 2.4 million nucleotides. RNAP produces RNA that, functionally, is either for protei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription Preinitiation Complex
The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription (genetics), transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA polymerase II (Pol II) at gene transcription start sites, DNA melting, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription. The minimal PIC includes RNA polymerase II and six general transcription factors: Transcription factor II A, TFIIA, Transcription factor II B, TFIIB, Transcription factor II D, TFIID, Transcription factor II E, TFIIE, Transcription factor II F, TFIIF, and Transcription factor II H, TFIIH. Additional regulatory complexes (such as the mediator (coactivator), mediator coactivator and chromatin structure remodeling (RSC) complex, chromatin remodeling complexes) may also be components of the PIC. Preinitiation complexes are also formed during RNA Polymerase I and RNA Polymerase II ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varidnaviria
''Varidnaviria'' is a realm of viruses that includes all DNA viruses that encode major capsid proteins that contain two vertical jelly roll folds. The major capsid proteins (MCP) form into pseudohexameric subunits of the viral capsid, which stores the viral deoxyribonucleic acid (DNA). The jelly roll folds are vertical, or perpendicular, to the surface of the capsid. Apart from the double jelly roll fold MCP (DJR-MCP), most viruses in the realm share many other characteristics, such as minor capsid proteins (mCP) that has one vertical jelly roll fold, an ATPase that packages viral DNA into the capsid, a DNA polymerase that replicates the viral genome, and capsids that are icosahedral in shape. ''Varidnaviria'' was established in 2019 based on the shared characteristics of the viruses in the realm. There are two kingdoms in the realm: ''Abadenavirae'', which contains all prokaryotic DJR-MCP viruses except tectiviruses, and ''Bamfordvirae'' which contains tectiviruses and al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
