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Orthornavirae
''Orthornavirae'' is a kingdom of viruses that have genomes made of ribonucleic acid (RNA), those genomes encoding an RNA-dependent RNA polymerase (RdRp). The RdRp is used to transcribe the viral RNA genome into messenger RNA (mRNA) and to replicate the genome. Viruses in this kingdom also share a number of characteristics involving evolution, including high rates of genetic mutations, recombinations, and reassortments. Viruses in ''Orthornavirae'' belong to the realm ''Riboviria''. They are descended from a common ancestor that may have been a non-viral molecule that encoded a reverse transcriptase instead of an RdRp for replication. The kingdom is subdivided into five phyla that separate member viruses based on their genome type, host range, and genetic similarity. Viruses with three genome types are included: positive-strand RNA viruses, negative-strand RNA viruses, and double-stranded RNA viruses. Many of the most widely known viral diseases are caused by RNA viruses in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riboviria
''Riboviria'' is a realm of viruses that includes all viruses that use a homologous RNA-dependent polymerase for replication. It includes RNA viruses that encode an RNA-dependent RNA polymerase, as well as reverse-transcribing viruses (with either RNA or DNA genomes) that encode an RNA-dependent DNA polymerase. RNA-dependent RNA polymerase (RdRp), also called RNA replicase, produces RNA (ribonucleic acid) from RNA. RNA-dependent DNA polymerase (RdDp), also called reverse transcriptase (RT), produces DNA ( deoxyribonucleic acid) from RNA. These enzymes are essential for replicating the viral genome and transcribing viral genes into messenger RNA (mRNA) for translation of viral proteins. ''Riboviria'' was established in 2018 to accommodate all RdRp-encoding RNA viruses and was expanded a year later to also include RdDp-encoding retroviruses. These two groups of viruses are assigned to two separate kingdoms: ''Orthornavirae'' for RdRp-encoding RNA viruses, and ''Pararnavirae'' for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Negarnaviricota
Negative-strand RNA viruses (−ssRNA viruses) are a group of related viruses that have negative-sense, single-stranded genomes made of ribonucleic acid. They have genomes that act as complementary strands from which messenger RNA (mRNA) is synthesized by the viral enzyme RNA-dependent RNA polymerase (RdRp). During replication of the viral genome, RdRp synthesizes a positive-sense antigenome that it uses as a template to create genomic negative-sense RNA. Negative-strand RNA viruses also share a number of other characteristics: most contain a viral envelope that surrounds the capsid, which encases the viral genome, −ssRNA virus genomes are usually linear, and it is common for their genome to be segmented. Negative-strand RNA viruses constitute the phylum ''Negarnaviricota'', in the kingdom ''Orthornavirae'' and realm ''Riboviria''. They are descended from a common ancestor that was a double-stranded RNA (dsRNA) virus, and they are considered to be a sister clade of reoviruses, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Negative-strand RNA Virus
Negative-strand RNA viruses (−ssRNA viruses) are a group of related viruses that have negative-sense, single-stranded genomes made of ribonucleic acid. They have genomes that act as complementary strands from which messenger RNA (mRNA) is synthesized by the viral enzyme RNA-dependent RNA polymerase (RdRp). During replication of the viral genome, RdRp synthesizes a positive-sense antigenome that it uses as a template to create genomic negative-sense RNA. Negative-strand RNA viruses also share a number of other characteristics: most contain a viral envelope that surrounds the capsid, which encases the viral genome, −ssRNA virus genomes are usually linear, and it is common for their genome to be segmented. Negative-strand RNA viruses constitute the phylum ''Negarnaviricota'', in the kingdom '' Orthornavirae'' and realm '' Riboviria''. They are descended from a common ancestor that was a double-stranded RNA (dsRNA) virus, and they are considered to be a sister clade of reovi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double-stranded RNA Viruses
Double-stranded RNA viruses (dsRNA viruses) are a polyphyletic group of viruses that have double-stranded genomes made of ribonucleic acid. The double-stranded genome is used to transcribe a positive-strand RNA by the viral RNA-dependent RNA polymerase (RdRp). The positive-strand RNA may be used as messenger RNA (mRNA) which can be translated into viral proteins by the host cell's ribosomes. The positive-strand RNA can also be replicated by the RdRp to create a new double-stranded viral genome. Double-stranded RNA viruses are classified in two separate phyla ''Duplornaviricota'' and ''Pisuviricota'' (specifically class ''Duplopiviricetes''), which are in the kingdom ''Orthornavirae'' and realm ''Riboviria''. The two groups do not share a common dsRNA virus ancestor. Double-stranded RNA viruses evolved two separate times from positive-strand RNA viruses. In the Baltimore classification system, dsRNA viruses belong to Group III. Virus group members vary widely in host range (anim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Positive-strand RNA Virus
Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can be directly translated into viral proteins by the host cell's ribosomes. Positive-strand RNA viruses encode an RNA-dependent RNA polymerase (RdRp) which is used during replication of the genome to synthesize a negative-sense antigenome that is then used as a template to create a new positive-sense viral genome. Positive-strand RNA viruses are divided between the phyla ''Kitrinoviricota'', ''Lenarviricota'', and ''Pisuviricota'' (specifically classes ''Pisoniviricetes'' and '' Stelpavirictes'') all of which are in the kingdom '' Orthornavirae'' and realm '' Riboviria''. They are monophyletic and descended from a common RNA virus ancestor. In the Baltimore classification system, +ssRNA viruses belong to Group IV. Positive-sense RNA viruses include pathogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pisuviricota
''Pisuviricota'' is a phylum of RNA viruses that includes all positive-strand and double-stranded RNA viruses that infect eukaryotes and are not members of the phylum ''Kitrinoviricota,'' ''Lenarviricota'' or ''Duplornaviricota.'' The name of the group is a syllabic abbreviation of “''pi''cornavirus ''su''pergroup” with the suffix ''-viricota'', indicating a virus phylum. Phylogenetic analyses suggest that ''Birnaviridae'' and ''Permutotetraviridae'', both currently unassigned to a phylum in ''Orthornavirae'', also belong to this phylum and that both are sister groups. Another proposed family of the phylum is unassigned '' Polymycoviridae'' in ''Riboviria''.Suvi Sutela, Anna Poimala, Eeva J Vainio (2019)Viruses of fungi and oomycetes in the soil environment Oxford Academic. Classes The following classes are recognized: * ''Duplopiviricetes'' * ''Pisoniviricetes'' * ''Stelpaviricetes ''Stelpaviricetes'' is a class of non-enveloped, positive-strand RNA viruses which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribonucleic Acid
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydrates, nucleic acids constitute one of the four major macromolecules essential for all known forms of life. Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA, RNA is found in nature as a single strand folded onto itself, rather than a paired double strand. Cellular organisms use messenger RNA (''mRNA'') to convey genetic information (using the nitrogenous bases of guanine, uracil, adenine, and cytosine, denoted by the letters G, U, A, and C) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome. Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular sign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteriophage Qβ
Bacteriophage Qbeta (''Qubevirus durum''), commonly referred to as Qbeta or Qβ, is a positive-strand RNA virus which infects bacteria that have F-pili, most commonly ''Escherichia coli''. Its linear genome is packaged into an icosahedral capsid with a diameter of 28 nm. Bacteriophage Qβ enters its host cell after binding to the side of the F-pilus. Genetics The genome of Qβ is approximately 4,217 nucleotides, depending on the source which sequenced the virus. Qβ has been isolated all over the world, multiple times, with various subspecies that code for nearly identical proteins but can have very different nucleotide sequences. The genome has three open reading frames that encode four proteins: the maturation/lysis protein A2; the coat protein; a readthrough of a leaky stop codon in the coat protein, called A1; and the β-subunit of an RNA-dependent RNA-polymerase (RdRp) termed the replicase. The genome is highly structured, regulating gene expression and protecting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reassortment
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. If a single host (a human, a chicken, or other animal) is infected by two different strains of the influenza virus, then it is possible that new assembled viral particles will be created from segments whose origin is mixed, some coming from one strain and some coming from another. The new reassortant strain will share properties of both of its parental lineages. Reassortment is responsible for some of the major ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Recombination
Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be further passed on from parents to offspring. Most recombination occurs naturally and can be classified into two types: (1) ''interchromosomal'' recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) ''intrachromosomal'' recombination, occurring through crossing over. During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication (translesion synthesis). Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics (phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity. Mutation is the ultimate source o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Evolution
Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates (on the order of one point mutation or more per genome per round of replication). Although most viral mutations confer no benefit and often even prove deleterious to viruses, the rapid rate of viral mutation combined with natural selection allows viruses to quickly adapt to changes in their host environment. In addition, because viruses typically produce many copies in an infected host, mutated genes can be passed on to many offspring quickly. Although the chance of mutations and evolution can change depending on the type of virus (e.g., double stranded DNA, double stranded RNA, single strand DNA), viruses overall have high chances for mutations. Viral evolution is an important aspect of the epidemiology of viral diseases such as influenza (influ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
