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L-A Helper Virus
''Saccharomyces cerevisiae virus L-A'', also called L-A helper virus, is a member of the ''Totiviridae'' family of viruses found primarily in ''Saccharomyces cerevisiae''. Its discovery in the 1970s was the main starting point of research on yeast virology. It is a ~4.6 kb double-stranded RNA virus with no extracellular phase and so is inherited through vertical cytoplasmic transmission. Additionally, in many strains of the yeast, it is found along with another virus called the M virus (or "M dsRNA", "Saccharomyces cerevisiae killer virus"), known to encode the killer toxin in many ''S. cerevisiae'' strains which confers the ability to kill neighboring sensitive cells that do not harbor the virus. It is indeed for this reason the virus is referred to as a helper virus, due to the M genome's dependence on it for its own survival and replication. (More recently, the M dsRNA is described as a satellite RNA.) A Yeast lineage with a M/killer virus is known as a " killer strain". Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Totiviridae
''Totiviridae'' is a family of double-stranded RNA viruses. Giardia lamblia, leishmania, trichomonas vaginalis, and fungi serve as natural hosts. The name of the group derives from Latin ''toti'' which means undivided or whole. There are 28 species in this family, assigned to 5 genera. Structure Viruses in the family ''Totiviridae'' are non-enveloped, double-stranded RNA viruses with icosahedral geometries, and T=2 symmetry. The virion consists of a single capsid protein and is about 40 nanometers in diameter. Genome The genome is composed of a monopartite, linear double-stranded RNA molecule of 4.6–6.7 kilobases. It contains two overlapping open reading frames (ORF) – ''gag'' and ''pol –'' which respectively encode the capsid protein and the RNA-dependent RNA polymerase. Some totiviruses contain a third small potential ORF. Life cycle Viral replication is cytoplasmic. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saccharomyces Cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular biology, molecular and cell biology, much like ''Escherichia coli'' as the model bacteria, bacterium. It is the microorganism behind the most common type of fermentation (biochemistry), fermentation. ''S. cerevisiae'' cells are round to ovoid, 5–10 micrometre, μm in diameter. It reproduces by budding. Many proteins important in human biology were first discovered by studying their Homology (biology), homologs in yeast; these proteins include cell cycle proteins, signaling proteins, and protein-processing enzymes. ''S. cerevisiae'' is currently the only yeast cell known to have Berkeley body, Berkeley bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilobase
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA. Dictated by specific hydrogen bonding patterns, "Watson–Crick" (or "Watson–Crick–Franklin") base pairs (guanine–cytosine and adenine–thymine) allow the DNA helix to maintain a regular helical structure that is subtly dependent on its nucleotide sequence. The complementary nature of this based-paired structure provides a redundant copy of the genetic information encoded within each strand of DNA. The regular structure and data redundancy provided by the DNA double helix make DNA well suited to the storage of genetic information, while base-pairing between DNA and incoming nucleotides provides the mechanism through which DNA polymerase replicates DNA and RNA polymerase transcribes DNA into RNA. Many DNA-binding proteins ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double-stranded RNA Virus
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] |
Vertical Transmission
Vertical transmission of symbionts is the transfer of a microbial symbiont from the parent directly to the offspring. Many metazoan species carry symbiotic bacteria which play a mutualistic, commensal, or parasitic role. A symbiont is acquired by a host via horizontal, vertical, or mixed transmission. Implications Complex interdependence occurs between host and symbiont. The genetic pool of the symbiont is generally smaller and more subject to genetic drift. In true vertical transmission, the evolutionary outcomes of the host and symbiont are linked. If there is mixed transmission, new genetic material may be introduced. Generally, symbionts settle into specific niches and can even transfer part of their genome into the host nucleus. Evolutionary consequences Benefits The mechanism promotes tightly coupled evolutionary pressure, which causes the host and symbiont to function as a holobiont. Disadvantages Evolutionary bottlenecks lead to less symbiont diversity, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helper Virus
A helper virus is a virus that allows an otherwise-deficient coinfecting virus to replicate. These can be naturally occurring as with Hepatitis D virus, which requires Hepatitis B virus to coinfect cells in order to replicate. Helper viruses are also commonly used to replicate and spread viral vectors for gene expression and gene therapy. See also * Helper dependent virus * Virophage Virophages are small, double-stranded DNA viral phages that require the Coinfection, co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant ... References Virology {{virus-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of 'junk' DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplasts with a chloroplast genome. The study of the genome is called genomics. The genomes of many organisms have been sequenced and various regions have been annotated. The International Human Genome Project reported the sequence of the genome for ''Homo sapiens'' in 200The Human Genome Project although the initial "finished" sequence was missing 8% of the genome consisting mostly of repetitive sequences. With advancements in technology that could handle sequenci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite RNA
A satellite is a subviral agent that depends on the coinfection of a host cell with a helper virus for its replication. Satellites can be divided into two major classes: satellite viruses and satellite nucleic acids. Satellite viruses, which are most commonly associated with plants, are also found in mammals, arthropods, and bacteria. They encode structural proteins to enclose their genetic material, which are therefore distinct from the structural proteins of their helper viruses. Satellite nucleic acids, in contrast, do not encode their own structural proteins, but instead are encapsulated by proteins encoded by their helper viruses. The genomes of satellites range upward from 359 nucleotides in length for satellite tobacco ringspot virus RNA (STobRV). Most viruses have the capability to use host enzymes or their own replication machinery to independently replicate their own viral RNA. Satellites, in contrast, are completely dependent on a helper virus for replication. The symb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Killer Yeast
A killer yeast is a yeast, such as ''Saccharomyces cerevisiae'', which is able to secrete one of a number of toxic proteins which are lethal to susceptible cells. These "killer toxins" are polypeptides that kill sensitive cells of the same or related species, often functioning by creating pores in target cell membranes. These yeast cells are immune to the toxic effects of the protein due to an intrinsic immunity. Killer yeast strains can be a problem in commercial processing because they can kill desirable strains. The killer yeast system was first described in 1963. Study of killer toxins helped to better understand the secretion pathway of yeast, which is similar to those of more complex eukaryotes. It also can be used in treatment of some diseases, mainly those caused by fungi. ''Saccharomyces cerevisiae'' The best characterized toxin system is from yeast (''Saccharomyces cerevisiae''), which was found to spoil brewing of beer. In ''S. cerevisiae'' are toxins encoded by a doub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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