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Synthesis-dependent Strand Annealing (SDSA)
Synthesis-dependent strand annealing (SDSA) is a major mechanism of homology-directed repair of DNA double-strand breaks (DSBs). Although many of the features of SDSA were first suggested in 1976, the double-Holliday junction model proposed in 1983 was favored by many researchers. In 1994, studies of double-strand gap repair in ''Drosophila'' were found to be incompatible with the double-Holliday junction model, leading researchers to propose a model they called synthesis-dependent strand annealing. Subsequent studies of meiotic recombination in ''S. cerevisiae'' found that non-crossover products appear earlier than double-Holliday junctions or crossover products, challenging the previous notion that both crossover and non-crossover products are produced by double-Holliday junctions and leading the authors to propose that non-crossover products are generated through SDSA. In the accompanying Figure, the first step labeled “5’ to 3’ resection” shows the formation of a 3’ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homologous Recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in Cell (biology), cellular organisms but may be also RNA in viruses). Homologous recombination is widely used by cells to accurately DNA repair, repair harmful DNA breaks that occur on both strands of DNA, known as double-strand breaks (DSB), in a process called homologous recombinational repair (HRR). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and ovum, egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to Adaptation, adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sordaria Fimicola
''Sordaria fimicola'' is a species of microscopic fungus. It is commonly found in the feces of herbivores. ''Sordaria fimicola'' is often used in introductory biology and mycology labs because it is easy to grow on nutrient agar in dish cultures. The genus ''Sordaria'', closely related to ''Neurospora'' and ''Podospora'', is a member of the large class Sordariomycetes, or flask-fungi. The natural habitat of the three species of ''Sordaria'' that have been the principal subjects in genetic studies is dung of herbivorous animals. The species ''S. fimicola'' is common and worldwide in distribution. The species of ''Sordaria'' are similar morphologically, producing black perithecia containing asci with eight dark ascospores in a linear arrangement. These species share a number of characteristics that are advantageous for genetic studies. They all have a short life cycle, usually 7–12 days, and are easily grown in culture. Most species are self-fertile and each strain is is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Podospora Anserina
''Podospora anserina'' is a filamentous ascomycete fungus from the order Sordariales. It is considered a model organism for the study of molecular biology of senescence (aging), prions, sexual reproduction, and meiotic drive. It has an obligate sexual and pseudohomothallic life cycle. It is a non-pathogenic coprophilous fungus that colonizes the dung of herbivorous animals such as horses, rabbits, cows and sheep. Taxonomy ''Podospora anserina'' was originally named ''Malinvernia anserina'' Rabenhorst (1857). ''Podospora anserina'' was subsequently published in Niessl (1883), which is used today to reference the common laboratory strain therefrom, 'Niessl'. It is also known as ''Pleurage anserina'' (Ces.) Kuntze. Genetics of ''P. anserina'' were characterized in Rizet and Engelmann (1949) and reviewed by Esser (1974). ''P. anserina'' is estimated to have diverged from ''Neurospora crassa'' 75 million years ago based on 18S rRNA and protein orthologous share 60-70% homology. G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome of around 135 Base pair#Length measurements, megabase pairs. It was the first plant to have its genome sequenced, and is an important tool for understanding the molecular biology of many plant traits, including flower development and phototropism, light sensing. Description ''Arabidopsis thaliana'' is an annual plant, annual (rarely biennial plant, biennial) plant, usually growing to 20–25 cm tall. The leaf, leaves form a rosette at the base of the plant, with a few leaves also on the flowering Plant ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caenorhabditis Elegans
''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a Hybrid word, blend of the Greek ''caeno-'' (recent), ''rhabditis'' (rod-like) and Latin ''elegans'' (elegant). In 1900, Émile Maupas, Maupas initially named it ''Rhabditidae, Rhabditides elegans.'' Günther Osche, Osche placed it in the subgenus ''Caenorhabditis'' in 1952, and in 1955, Ellsworth Dougherty, Dougherty raised ''Caenorhabditis'' to the status of genus. ''C. elegans'' is an unsegmented pseudocoelomate and lacks respiratory or circulatory systems. Most of these nematodes are hermaphrodites and a few are males. Males have specialised tails for mating that include spicule (nematode), spicules. In 1963, Sydney Brenner proposed research into ''C. elegans,'' primarily in the area of neuronal development. In 1974, he began research into the molecular biology, molecular and developmental ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RMI1
RecQ-mediated genome instability protein 1 is a protein that in humans is encoded by the ''RMI1'' gene. Genetic disorders Mutations in RMI1 are associated with Bloom-Syndrome like disorder. Two patients, both with microcephalic dwarfism came from the same family. They carried identical heterozygous mutations: 255_1259delLys419LeufsTer5]. Function RMI1 protein is a component of the Bloom Syndrome Complex. RMI1 protein is made up of 2 OB (oligonucleotide binding) domains. OB1 binds to TOP3A, Topoisomerase III alpha, while OB2 binds to RMI2 within the Bloom Syndrome complex, and FANCM of the Fanconi Anaemia pathway. An insert within OB1 domain of RMI1 inserts into the catalytic centre of Topoisomerase III alpha, and is necessary for the optimal activity of this enzyme during cellular DNA repair and homologous recombination. Meiosis During meiosis in budding yeast ''Saccharomyces cerevisiae'', TOP3 (a type I topoisomerase) and its accessory factor RMI1 form a heterodimer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TOP3A
DNA topoisomerase 3-alpha is an enzyme that in humans is encoded by the ''TOP3A'' gene. Function This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells. Meiosis Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called ''resection''. In the ''strand invasion'' step that follows, an overhanging 3' end of the broken DNA molecule then "invades" the DNA of an homologous chromosome that is not broken forming a displacement loop (D-loop). After strand invasion, the further sequ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (biology)
In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained heredity from a common descent, common ancestor after having been subjected to adaptation (biology), adaptive modifications for different purposes as the result of natural selection. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this from Aristotle's biology onwards, and it was explicitly analysed by Pierre Belon in 1555. A common example of homologous structures is the forelimbs of vertebrates, where the bat wing development, wings of bats and origin of avian flight, birds, the arms of primates, the front flipper (anatomy), flippers of whales, and the forelegs of quadrupedalis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bloom Syndrome Protein
Bloom syndrome protein is a protein that in humans is encoded by the ''BLM'' gene and is not expressed in Bloom syndrome. The Bloom syndrome gene product is related to the RecQ subset of DExH box-containing DNA helicases and has both DNA-stimulated ATPase and ATP-dependent DNA helicase activities. Mutations causing Bloom syndrome delete or alter helicase motifs and may disable the 3' → 5' helicase activity. The normal protein may act to suppress inappropriate homologous recombination. Meiosis Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called resection. In the strand invasion step that follows, an overhanging 3' end of the broken DNA molecule then "invades" the DNA of an homologous chromosome that is not broken. After strand invasion, the further sequence of events may follow either of two main pathways leading to a crossover (CO) or a non-cros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Replication Protein A
Replication protein A (RPA) is the major protein that binds to single-stranded DNA (ssDNA) in eukaryotic cells. In vitro, RPA shows a much higher affinity for ssDNA than RNA or double-stranded DNA. RPA is required in replication, recombination and repair processes such as nucleotide excision repair and homologous recombination. It also plays roles in responding to damaged DNA. Structure RPA is a heterotrimer, composed of the subunits RPA1 (RPA70) (70kDa subunit), RPA2 (RPA32) (32kDa subunit) and RPA3 (RPA14) (14kDa subunit). The three RPA subunits contain six OB-folds (oligonucleotide/oligosaccharide binding), with DNA-binding domains (DBD) designated DBDs A-F, that bind RPA to single-stranded DNA. DBDs A, B, C and F are located on RPA1, DBD D is located on RPA2, and DBD E is located on RPA3. DBDs C, D, and E make up the trimerization core of the protein with flexible linker regions connecting them all together. Due to these flexible linker regions RPA is consider ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DMC1 (gene)
Meiotic recombination protein DMC1/LIM15 homolog is a protein that in humans is encoded by the ''DMC1'' gene. Meiotic recombination protein Dmc1 is a homolog of the bacterial strand exchange protein RecA. Dmc1 plays the central role in homologous recombination in meiosis by assembling at the sites of programmed DNA double strand breaks and carrying out a search for allelic DNA sequences located on homologous chromatids. The name "Dmc" stands for "disrupted meiotic cDNA" and refers to the method used for its discovery which involved using clones from a meiosis-specific cDNA library to direct knock-out mutations of abundantly expressed meiotic genes The Dmc1 protein is one of two homologs of RecA found in eukaryotic cells, the other being Rad51. DMC1 and RAD51 share over 50% amino acid similarity. In budding yeast, Rad51 serves as a strand exchange protein in mitosis where it is critical for the repair of DNA breaks. Rad51 is converted to an accessory factor for Dmc1 during mei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
