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Type III and type IV secretion systems, which are both expressed in Gram-negative bacteria, are the secretion systems most frequently linked to PAIs. The bacterial membranes contain the type III secretion system (T3SS), which functions essentially as a molecular syringe. The needle-like apparatus secretes effectors, wh...
Wikipedia - Pathogenicity island - Properties
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Section: Examples. The P fimbriae island contains virulence factors such as haemolysin, pili, cytotoxic necrosing factor, and uropathogenic specific protein (USP). Yersinia pestis high pathogenicity island I has genes regulating iron uptake and storage. Salmonella SP-1 and SP-2 sites regulates bacterium's invasion and ...
Wikipedia - Pathogenicity island - Examples
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Article: Penetrance. Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (genotype) that also expresses an associated trait (phenotype). In medical genetics, the penetrance of a disease-causing mutation is the proportion of individuals with the mutation that exhib...
Wikipedia - Penetrance - Summary
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Section: Degrees of penetrance > Reduced penetrance. The penetrance is said to be reduced if less than 100% of individuals carrying a particular genotype express associated traits, and is likely to be caused by a combination of genetic, environmental and lifestyle factors. BRCA1 is an example of a genotype with reduced...
Wikipedia - Penetrance - Degrees of penetrance > Reduced penetrance
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Section: Factors affecting penetrance > Age-dependent penetrance. If clinical signs associated with a specific genotype appear more frequently with increasing age, the penetrance is said to be age dependent. Some diseases are non-penetrant up until a certain age and then the penetrance starts to increase drastically, w...
Wikipedia - Penetrance - Factors affecting penetrance > Age-dependent penetrance
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Section: Factors affecting penetrance > Gender-related penetrance. For some mutations, the phenotype is more frequently present in one sex and in rare cases mutations appear completely non-penetrant in a particular gender. This is called gender-related penetrance or sex-dependent penetrance and may be the result of all...
Wikipedia - Penetrance - Factors affecting penetrance > Gender-related penetrance
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Section: Factors affecting penetrance > Epigenetic regulation. Sometimes, genetic alterations which can cause genetic disease and phenotypic traits, are not from changes related directly to the DNA sequence, but from epigenetic alterations such as DNA methylation or histone modifications. Epigenetic differences may the...
Wikipedia - Penetrance - Factors affecting penetrance > Epigenetic regulation
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Section: Determining penetrance > Ascertainment bias. Penetrance estimates can be affected by ascertainment bias if the sampling is not systematic. Traditionally a phenotype-driven approach focusing on individuals with a given condition and their family members has been used to determine penetrance. However, it may be ...
Wikipedia - Penetrance - Determining penetrance > Ascertainment bias
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Section: Determining penetrance > Phenocopies. A genotype with complete penetrance will always display the clinical phenotypic traits related to its mutation (taking into consideration the expressivity), but the signs or symptoms displayed by a specific affected individual can often be similar to other unrelated phenot...
Wikipedia - Penetrance - Determining penetrance > Phenocopies
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Section: Phene - phenotype - phenome distinction. The term 'phene' was evidently coined as an obvious parallel construct to 'gene'. Phene is to Phenotype as Gene is to Genotype, and Similarly Phene is to Phenome as Gene is to Genome. More specifically, a Phene is an abstract concept describing a particular characterist...
Wikipedia - Phene - Phene - phenotype - phenome distinction
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It is important to note that the word phenotype was originally used to refer to both the trait/character itself (e.g. the blue eyes phenotype) and the set of traits/characteristics possessed by the organism (clair's eye-colour phenotype is blue). While this definition is still used in many places, the lack of distincti...
Wikipedia - Phene - Phene - phenotype - phenome distinction
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Section: Phene - gene distinction. Genes give rise to phenes. Genes are the biochemical instructions encoding what an organism can be, while phenes are what the organism is. In general it takes a combination of particular genes, environmental influences and random variation to give rise to any one phene in an organism....
Wikipedia - Phene - Phene - gene distinction
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Section: Examples. The butterfly genus Vanessa can change phenotype based on the local temperature. If introduced to Lapland they mimic butterflies localised to this area; and if localised to Syria they mimic butterflies of this area. The larvae of Drosophila melanogaster have been found to be particularly vulnerable t...
Wikipedia - Phenocopy - Examples
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Article: Phenotypic integration. Phenotypic integration is a metric for measuring the correlation of multiple functionally-related traits to each other. Complex phenotypes often require multiple traits working together in order to function properly. Phenotypic integration is significant because it provides an explanati...
Wikipedia - Phenotypic integration - Summary
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Section: Origins. Shortly after the structure of DNA was uncovered, Everett C. Olson and Robert L. Miller (1958) wrote the first book regarding the topic of phenotypic integration. The term integration was first used in reference to genetics by Olson and Miller, referring to correlations among characters that are influ...
Wikipedia - Phenotypic integration - Origins
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Section: Natural Selection and Phenotypic Integration. Phenotypic Integration can be favorable or unfavorable with respect to natural selection. It has been shown that certain combinations of correlated traits can be unfavorable to an organism. In an ontogenetic study of laboratory rats, certain covariances among devel...
Wikipedia - Phenotypic integration - Natural Selection and Phenotypic Integration
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Section: Evolution of Phenotypic Integration. Integration can be found at the genetic level due to genetic linkage. Genetic linkage involves multiple genes being inherited together during meiosis because they are close to each other on the same chromosome. Alleles at different loci can be inherited together if they are...
Wikipedia - Phenotypic integration - Evolution of Phenotypic Integration
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Evolution may also occur because the integration may have an adaptive advantage in a particular environment for an organism. It is also important to recognize that not only can the traits be inherited together, but inherited separately and selected together. Another important example of phenotypic integration evolving ...
Wikipedia - Phenotypic integration - Evolution of Phenotypic Integration
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Section: Examples. Aposematism in poison dart frogs has also shown that phenotypic integration may be involved. Aposematism is the use of warning colors to deter predators because it often conveys the organism being poisonous, and this study found that diet specialization, and chemical defense are integrated and help a...
Wikipedia - Phenotypic integration - Examples
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Article: Phenotypic plasticity. Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induce...
Wikipedia - Phenotypic plasticity - Summary
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Section: Examples > Plants. Phenotypic plasticity in plants includes the timing of transition from vegetative to reproductive growth stage, the allocation of more resources to the roots in soils that contain low concentrations of nutrients, the size of the seeds an individual produces depending on the environment, and ...
Wikipedia - Phenotypic plasticity - Examples > Plants
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Section: Examples > Phytohormones and leaf plasticity. Leaves are very important to a plant in that they create an avenue where photosynthesis and thermoregulation can occur. Evolutionarily, the environmental contribution to leaf shape allowed for a myriad of different types of leaves to be created. Leaf shape can be d...
Wikipedia - Phenotypic plasticity - Examples > Phytohormones and leaf plasticity
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The Genetic Regulatory Network is responsible for creating this phenotypic plasticity and involves a variety of genes and proteins regulating leaf morphology. Phytohormones have been shown to play a key role in signaling throughout the plant, and changes in concentration of the phytohormones can cause a change in devel...
Wikipedia - Phenotypic plasticity - Examples > Phytohormones and leaf plasticity
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Section: Examples > Animals. The developmental effects of nutrition and temperature have been demonstrated. The gray wolf (Canis lupus) has wide phenotypic plasticity. Additionally, male speckled wood butterflies have two morphs: one with three dots on its hindwing, and one with four dots on its hindwings. The developm...
Wikipedia - Phenotypic plasticity - Examples > Animals
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Section: Examples > Animals > Diet. Phenotypic plasticity of the digestive system allows some animals to respond to changes in dietary nutrient composition, diet quality, and energy requirements. Changes in the nutrient composition of the diet (the proportion of lipids, proteins and carbohydrates) may occur during deve...
Wikipedia - Phenotypic plasticity - Examples > Animals > Diet
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prairie voles, Mongolian gerbils, Japanese quail, wood ducks, mallards). Poor quality diets also result in lower concentrations of nutrients in the lumen of the intestine, which can cause a decrease in the activity of several digestive enzymes. Animals often consume more food during periods of high energy demand (e.g. ...
Wikipedia - Phenotypic plasticity - Examples > Animals > Diet
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Section: Examples > Animals > Parasitism. Infection with parasites can induce phenotypic plasticity as a means to compensate for the detrimental effects caused by parasitism. Commonly, invertebrates respond to parasitic castration or increased parasite virulence with fecundity compensation in order to increase their re...
Wikipedia - Phenotypic plasticity - Examples > Animals > Parasitism
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Phenotypic plasticity can also be observed as changes in behaviour. In response to infection, both vertebrates and invertebrates practice self-medication, which can be considered a form of adaptive plasticity. Various species of non-human primates infected with intestinal worms engage in leaf-swallowing, in which they ...
Wikipedia - Phenotypic plasticity - Examples > Animals > Parasitism
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Reproduction The red-eyed tree frog, Agalychnis callidryas, is an arboreal frog (hylid) that resides in the tropics of Central America. Unlike many frogs, the red-eyed tree frog has arboreal eggs which are laid on leaves hanging over ponds or large puddles and, upon hatching, the tadpoles fall into the water below. One...
Wikipedia - Phenotypic plasticity - Examples > Animals > Parasitism
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Section: Evolution. Plasticity is usually thought to be an evolutionary adaptation to environmental variations that is reasonably predictable and occurs within the lifespan of an individual organism, as it allows individuals to 'fit' their phenotype to different environments. If the optimal phenotype in a given environ...
Wikipedia - Phenotypic plasticity - Evolution
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These changes, in the absence of a predator, make the snails susceptible to other predators and limit fecundity. Therefore, these freshwater snails produce either an adaptive or maladaptive response to the environmental cue depending on whether predatory sunfish are present or not. Given the profound ecological importa...
Wikipedia - Phenotypic plasticity - Evolution
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Section: Plasticity and climate change. Unprecedented rates of climate change are predicted to occur over the next 100 years as a result of human activity. Phenotypic plasticity is a key mechanism with which organisms can cope with a changing climate, as it allows individuals to respond to change within their lifetime....
Wikipedia - Phenotypic plasticity - Plasticity and climate change
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Article: Plant genetic resources. Plant genetic resources describe the variability within plants that comes from human and natural selection over millennia. Their intrinsic value mainly concerns agricultural crops (crop biodiversity). According to the 1983 revised International Undertaking on Plant Genetic Resources fo...
Wikipedia - Plant genetic resources - Summary
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Section: History. The first use of plant genetic resources dates to more than 10,000 years ago, when farmers selected from the genetic variation they found in wild plants to develop their crops. As human populations moved to different climates and ecosystems, taking the crops with them, the crops adapted to the new env...
Wikipedia - Plant genetic resources - History
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Section: Conservation. Plant genetic resource conservation has become increasingly important as more plants have become threatened or rare. At the same time, an exploding world population and rapid climate change have led humans to seek new resilient and nutritious crops. Plant conservation strategies generally combine...
Wikipedia - Plant genetic resources - Conservation
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In the 1960s and 1970s, more focus was put on the collection and conservation of plant genetic resources in face of genetic erosion by organizations such as the Rockefeller Foundation and the European Society of Breeding Research (EUCARPIA). A key event in the conservation of plant genetic resources was the establishme...
Wikipedia - Plant genetic resources - Conservation
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Section: Policy. In response to the growing awareness of the global value of and threat to biological diversity, the United Nations drafted the 1992 Convention on Biological Diversity (CBD), the first global multilateral treaty focused on the conservation and sustainable use of biodiversity. Article 15 of the CBD speci...
Wikipedia - Plant genetic resources - Policy
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Article: Plant–fungus horizontal gene transfer. Plant–fungus horizontal gene transfer is the movement of genetic material between individuals in the plant and fungus kingdoms. Horizontal gene transfer is universal in fungi, viruses, bacteria, and other eukaryotes. Horizontal gene transfer research often focuses on prok...
Wikipedia - Plant–fungus horizontal gene transfer - Summary
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Section: Mechanisms. Fungus–plant-mediated horizontal gene transfer can occur via phagotrophic mechanisms (mediated by phagotrophic eukaryotes) and nonphagotropic mechanisms. Nonphagotrophic mechanisms have been seen in the transmission of transposable elements, plastid-derived endosymbiotic gene transfer, prokaryote-d...
Wikipedia - Plant–fungus horizontal gene transfer - Mechanisms
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Section: Indicators of past horizontal gene transfer. Evidence for gene transfer between fungi and eukaryotes is discovered indirectly. Evidence is found in the unusual features of genetic elements. These features include: inconsistency between phylogeny across genetic elements, high DNA or amino acid similarity from p...
Wikipedia - Plant–fungus horizontal gene transfer - Indicators of past horizontal gene transfer
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Section: Examples > In rice. A fungus–plant pathway has been demonstrated in rice (Oryza sativa) through ancestral lineages. A phylogeny was constructed from 1689 identified genes and all homologs available from the rice genome (3177 gene families). Fourteen candidate plant–fungus horizontal gene transfer events were i...
Wikipedia - Plant–fungus horizontal gene transfer - Examples > In rice
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Section: Examples > Ancestral shikimate pathway. Some plants may have obtained the shikimate pathway from symbiotic fungi. Plant shikimate pathway enzymes share similarities to prokaryote homologs and could have ancestry from a plastid progenitor genome. It is possible that the shikimate pathway and the pentafunctional...
Wikipedia - Plant–fungus horizontal gene transfer - Examples > Ancestral shikimate pathway
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Section: Examples > Ancestral land plants. Fungi and bacteria could have contributed to the phenylpropanoid pathway in ancestral land plants for the synthesis of flavonoids and lignin through horizontal gene transfer. Phenylalanine ammonia lyase (PAL) is known to be present in fungi, such as Basidiomycota yeast like Rh...
Wikipedia - Plant–fungus horizontal gene transfer - Examples > Ancestral land plants
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Section: Examples > Gene transfer for enhanced intermediate and secondary metabolism. Sterigmatocystin gene transfer has been observed with Podospora anserina and Aspergillus. Horizontal gene transfer in Aspergillus and Podospora contributed to fungal metabolic diversity in secondary metabolism. Aspergillus nidulans pr...
Wikipedia - Plant–fungus horizontal gene transfer - Examples > Gene transfer for enhanced intermediate and secondary metabolism
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Section: Examples > Acquired pathogenic capabilities. In Stagonospora and Pyrenophora, as well as in Fusarium and Alternaria, horizontal gene transfer provides a powerful mechanism for fungi to acquire pathogenic capabilities to infect a new host plant. Horizontal gene transfer and interspecific hybridization between p...
Wikipedia - Plant–fungus horizontal gene transfer - Examples > Acquired pathogenic capabilities
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Article: Polar overdominance. Polar overdominance is a unique form of inheritance originally described in livestock, with relevant examples in humans and mice being discovered shortly after. The term polar is used to describe this type of overdominance because the phenotype of the heterozygote is more prevalent than th...
Wikipedia - Polar overdominance - Summary
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Section: Discovery. The first described occurrence of polar overdominance in sheep was shown after finding that a mutant allele, called callipyge (after Venus Callipyge), must be inherited from the father to cause a condition called muscle hypertrophy. Muscle hypertrophy in the offspring is caused by an increase in the...
Wikipedia - Polar overdominance - Discovery
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Section: Agricultural application. More and more studies have identified quantitative trait loci (QTL) that show evidence of genomic imprinting in farm animals other than sheep. After polar overdominant inheritance was discovered to be the cause of muscular hypertrophy in sheep, the ortholog for the human DLK1 gene (DL...
Wikipedia - Polar overdominance - Agricultural application
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Section: In humans. The term polar is used to describe this type of inheritance because the phenotype of one heterozygote is expressed at a level higher than other genotypes for the same locus including those displaying either homozygous geneotype. This unique form of inheritance has largely been studied in non-human m...
Wikipedia - Polar overdominance - In humans
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Article: Polygenic adaptation. Polygenic adaptation describes a process in which a population adapts through small changes in allele frequencies at hundreds or thousands of loci. Many traits in humans and other species are highly polygenic, i.e., affected by standing genetic variation at hundreds or thousands of loci. ...
Wikipedia - Polygenic adaptation - Summary
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Section: Examples of polygenic adaptation. Polygenic adaptation is presumed to be the dominant mode of adaptation in artificial selection, when plants or animals undergo rapid responses to selective pressures. However, in most cases the actual genetic loci involved are not yet known (but see e.g.,). At present the best...
Wikipedia - Polygenic adaptation - Examples of polygenic adaptation
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Article: Polyphenism. A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyphenism in animals, from having sex determined by the en...
Wikipedia - Polyphenism - Summary
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Section: Definition. A polyphenism is the occurrence of several phenotypes in a population, the differences between which are not the result of genetic differences. For example, crocodiles possess a temperature-dependent sex determining polyphenism, where sex is the trait influenced by variations in nest temperature. W...
Wikipedia - Polyphenism - Definition
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Section: Types > Sex determination. Sex-determining polyphenisms allow a species to benefit from sexual reproduction while permitting an unequal gender ratio. This can be beneficial to a species because a large female-to-male ratio maximizes reproductive capacity. However, temperature-dependent sex determination (as se...
Wikipedia - Polyphenism - Types > Sex determination
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Section: Types > Insect castes. The caste system of insects enables eusociality, the division of labor between non-breeding and breeding individuals. A series of polyphenisms determines whether larvae develop into queens, workers, and, in some cases soldiers. In the case of the ant, P. morrisi, an embryo must develop u...
Wikipedia - Polyphenism - Types > Insect castes
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Section: Types > Predator-induced. Predator-induced polyphenisms allow the species to develop in a more reproductively-successful way in a predator's absence, but to otherwise assume a more defensible morphology. However, this can fail if the predator evolves to stop producing the kairomone to which the prey responds. ...
Wikipedia - Polyphenism - Types > Predator-induced
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Section: Types > Resource. Organisms with resource polyphenisms show alternative phenotypes that allow differential use of food or other resources. One example is the western spadefoot toad, which maximizes its reproductive capacity in temporary desert ponds. While the water is at a safe level, the tadpoles develop slo...
Wikipedia - Polyphenism - Types > Resource
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Section: Evolution. A mechanism has been proposed for the evolutionary development of polyphenisms: A mutation results in a novel, heritable trait. The trait's frequency expands in the population, creating a population on which selection can act. Pre-existing (background) genetic variation in other genes results in phe...
Wikipedia - Polyphenism - Evolution
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Article: Polyploid complex. A polyploid complex, also called a diploid-polyploid complex, is a group of interrelated and interbreeding species that also have differing levels of ploidy that can allow interbreeding. A polyploid complex was described by E. B. Babcock and G. Ledyard Stebbins in their 1938 monograph The Am...
Wikipedia - Polyploid complex - Summary
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Section: Overview. The classical example is the Drosophila wm4 (speak white-mottled-4) translocation. In this mutation, an inversion on the X chromosome placed the white gene next to pericentric heterochromatin, or a sequence of repeats that becomes heterochromatic. Normally, the white gene is expressed in every cell o...
Wikipedia - Position-effect variegation - Overview
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Section: Etymology. PEV is a position effect because the change in position of a gene from its original position to somewhere near a heterochromatic region has an effect on its expression. The effect is the variegation in a particular phenotype i.e., the appearance of irregular patches of different colour(s), due to th...
Wikipedia - Position-effect variegation - Etymology
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Section: Mechanisms > cis-spreading. According to this model, the heterochromatin forces an altered chromatin conformation on the euchromatic region. Due to this, the transcriptional machinery cannot access the gene which leads to the inhibition of transcription. In other words, the heterochromatin spreads and causes g...
Wikipedia - Position-effect variegation - Mechanisms > cis-spreading
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Section: Suppression in Drosophila melanogaster. The mutations in mus genes are the candidates as PEV modifiers, as these genes are involved in chromosome maintenance and repair. Chromosome structure in the vicinity of the breakpoint appears to be an important determinant of the gene inactivation process. Six second ch...
Wikipedia - Position-effect variegation - Suppression in Drosophila melanogaster
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Article: Positional sequencing. Positional sequencing is a method of sequencing DNA that simultaneously generates information about both identity and location of nucleotide sequences. The method involves detecting the location of sequence specific recognition events (e.g., such as hybridization of probes of known seque...
Wikipedia - Positional sequencing - Summary
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Article: Primosome. In molecular biology, a primosome is a protein complex responsible for creating RNA primers on single stranded DNA during DNA replication. The primosome consists of seven proteins: DnaG primase, DnaB helicase, DnaC helicase assistant, DnaT, PriA, Pri B, and PriC. At each replication fork, the primos...
Wikipedia - Primosome - Summary
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Assembly is initiated by interactions of PriA and PriB with ssDNA and the pas. PriC, DnaB, DnaC, and DnaT then act on the PriAPriB- DNA complex to yield the primosome. Primosomes are nucleoproteins assemblies that activate DNA replication forks. Their primary role is to recruit the replicative helicase onto single-stra...
Wikipedia - Primosome - Summary
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Article: Pronucleus. A pronucleus (pl.: pronuclei) denotes the nucleus found in either a sperm or egg cell during the process of fertilization. The sperm cell undergoes a transformation into a pronucleus after entering the egg cell but prior to the fusion of the genetic material of both the sperm and egg. In contrast, ...
Wikipedia - Pronucleus - Summary
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Section: History. The pronucleus was discovered the 1870s microscopically using staining techniques combined with microscopes with improved magnification levels. The pronucleus was originally found during the first studies on meiosis. Edouard Van Beneden published a paper in 1875 in which he first mentions the pronucle...
Wikipedia - Pronucleus - History
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Section: Formation. The female pronucleus is the female egg cell once it has become a haploid cell, and the male pronucleus forms when the sperm enters into the female egg. While the sperm develops inside of the male testes, the sperm does not become a pronucleus until it decondenses quickly inside of the female egg. W...
Wikipedia - Pronucleus - Formation
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Section: Combination of male and female pronuclei. In sea urchins, the formation of the zygote starts with the fusion of both the inner and outer nuclei of the male and female pronuclei. It is unknown if one of the pronuclei start the combination of the two, or if the microtubules that help the dissolution of membranes...
Wikipedia - Pronucleus - Combination of male and female pronuclei
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Article: Proofreading (biology). The term proofreading is used in genetics to refer to the error-correcting processes, first proposed by John Hopfield and Jacques Ninio, involved in DNA replication, immune system specificity, and enzyme-substrate recognition among many other processes that require enhanced specificity....
Wikipedia - Proofreading (biology) - Summary
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Section: Bacteriophage T4 DNA polymerase. Bacteriophage (phage) T4 gene 43 encodes the phage's DNA polymerase replicative enzyme. Temperature-sensitive (ts) gene 43 mutants have been identified that have an antimutator phenotype, that is a lower rate of spontaneous mutation than wild type. Studies of one of these mutan...
Wikipedia - Proofreading (biology) - Bacteriophage T4 DNA polymerase
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Section: SARS-CoV-2 proofreading enzyme. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the COVID-19 pandemic. The SARS-CoV-2 RNA virus genome encodes a replication-and transcription complex, a multisubunit protein machine that carries out viral genome replication and transcripti...
Wikipedia - Proofreading (biology) - SARS-CoV-2 proofreading enzyme
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Section: Staining and microscopy. Microscopy can be used to visualize condensed chromosomes as they move through meiosis and mitosis. Various DNA stains are used to treat cells such that condensing chromosomes can be visualized as the move through prophase. The giemsa G-banding technique is commonly used to identify ma...
Wikipedia - Prophase - Staining and microscopy
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Section: Mitotic prophase > Formation of the mitotic spindle. Microtubules involved in the interphase scaffolding break down as the replicated centrosomes separate. The movement of centrosomes to opposite poles is accompanied in animal cells by the organization of individual radial microtubule arrays (asters) by each c...
Wikipedia - Prophase - Mitotic prophase > Formation of the mitotic spindle
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Section: Meiotic prophase > Prophase I. Prophase I is divided into five phases: leptotene, zygotene, pachytene, diplotene, and diakinesis. In addition to the events that occur in mitotic prophase, several crucial events occur within these phases such as pairing of homologous chromosomes and the reciprocal exchange of g...
Wikipedia - Prophase - Meiotic prophase > Prophase I
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Section: Meiotic prophase > Prophase I > Zygotene. In the second phase of prophase I, zygotene (from the Greek for "conjugation"), all maternally and paternally derived chromosomes have found their homologous partner.: 98 The homologous pairs then undergo synapsis,a process by which the synaptonemal complex (a proteina...
Wikipedia - Prophase - Meiotic prophase > Prophase I > Zygotene
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Section: Meiotic prophase > Prophase I > Pachytene. The third phase of prophase I, pachytene (from the Greek for "thick"), begins at the completion of synapsis.: 98 Chromatin has condensed enough that chromosomes can now be resolved in microscopy. Structures called recombination nodules form on the synaptonemal complex...
Wikipedia - Prophase - Meiotic prophase > Prophase I > Pachytene
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Section: Prophase I arrest. Female mammals and birds are born possessing all the oocytes needed for future ovulations, and these oocytes are arrested at the prophase I stage of meiosis. In humans, as an example, oocytes are formed between three and four months of gestation within the fetus and are therefore present at ...
Wikipedia - Prophase - Prophase I arrest
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Article: Proton coupled amino acid transporter. Proton-coupled amino acid transporters belong to the SLC26A5 family; they are protein receptors whose main function is the transmembrane movement of amino acids and their derivatives. This family of receptors is most commonly found within the luminal surface of the small ...
Wikipedia - Proton coupled amino acid transporter - Summary
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Section: Proton-coupled amino acid transporters 1 and 2. The molecular weight of Proton-coupled amino acid transporter 1 is 53.28 kDA; the molecular weight of Proton-coupled amino acid transporter 2 is 53.22 kDA. PAT1 has been found in lysosomes in brain neurons but also in the apical membrane of intestinal epithelial ...
Wikipedia - Proton coupled amino acid transporter - Proton-coupled amino acid transporters 1 and 2
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Section: Biochemistry. Unlike most amino acid transporters in the exchange of Na+ with amino acid symporters, proton-coupled amino acid transporters function as H+ with amino acid symporters. They are located within the luminal surface of the small intestine and within lysosomes, so their action functions in absorption...
Wikipedia - Proton coupled amino acid transporter - Biochemistry
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Section: Function. The function of proton-coupled amino acid transporters is the transmembrane movement of amino acids and their derivatives for absorption by the luminal surface of the small intestine or digestion by intralysosomal proteins. In Drosophila models, the expression of SLC family genes that code for proton...
Wikipedia - Proton coupled amino acid transporter - Function
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Section: Non-functional proton coupled amino acid transporter. In hereditary disease iminoglycinuria, there is a defect in the human proton-coupled amino acid transporter 1 and 2 genes which results in a defect in the absorption of proline and glycine. Iminoglycinuria is an autosomal recessive disorder of the renal tub...
Wikipedia - Proton coupled amino acid transporter - Non-functional proton coupled amino acid transporter
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Section: Clinical significance. PAT1 mRNA is expressed in the GI tract between the stomach and descending colon, but is generally absent in the esophagus, caecum, and rectum. This allows for different treatments that affect the affinity of the carrier protein for its substrates, giving the potential to treat various am...
Wikipedia - Proton coupled amino acid transporter - Clinical significance
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Article: Pseudoalleles. Pseudoallelism is a state in which two genes with similar functions are located so close to one another on a chromosome that they are genetically linked. This means that the two genes (pseudoalleles) are nearly always inherited together. Since the two genes have related functions, they may appea...
Wikipedia - Pseudoalleles - Summary
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Section: In translocation heterozygote. In translocation heterozygote, however, certain patterns of chromosome segregation during meiosis produce genetically unbalanced gametes that at fertilization become deleterious to the zygote. In a translocation heterozygote, the two haploid sets of chromosomes do not carry the s...
Wikipedia - Pseudolinkage - In translocation heterozygote
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Section: In translocation heterozygote > Adjacent-2 segregation pattern. Because of the unusual cruciform pairing configuration in translocation heterozygotes, nondisjunction of homologous centromeres occurs at a measurable but low rate. This nondisjunction produces an adjacent-2 segregation pattern in which the homolo...
Wikipedia - Pseudolinkage - In translocation heterozygote > Adjacent-2 segregation pattern
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Article: Q-system (genetics). Q-system is a genetic tool that allows to express transgenes in a living organism. Originally the Q-system was developed for use in the vinegar fly Drosophila melanogaster, and was rapidly adapted for use in cultured mammalian cells, zebrafish, worms and mosquitoes. The Q-system utilizes g...
Wikipedia - Q-system (genetics) - Summary
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Section: Origin. The Q-system is based on two out of the seven genes of the qa gene cluster of the bread fungus Neurospora crassa. The genes of the qa cluster are responsible for the catabolism of quinic acid, which is used by the fungus as a carbon source in conditions of low glucose. The cluster contains a transcript...
Wikipedia - Q-system (genetics) - Origin
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Section: Use in Drosophila > Basic use. The Q-system functions similarly to, and independently of, the GAL4/UAS and the LexA/LexAop systems. QF, QF2 and QF2w are analogous to GAL4 and LexA, and their expression is usually under the control of cell-type specific promoter, such as nsyb (to target neurons) or tubulin (to ...
Wikipedia - Q-system (genetics) - Use in Drosophila > Basic use
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Section: Use in other organisms. Q-system appeared to be working successfully in a variety of organisms. It has been used to drive expression of luciferase, as a proof of principle, in cultured mammalian cells. In zebrafish the Q-system has been successfully used with several tissue-specific promoters, and was shown to...
Wikipedia - Q-system (genetics) - Use in other organisms
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Article: Radiation reduced hybrid. Radiation reduced hybrid is procedure in discovering the location of genetic markers relative to one another. The relative location of these markers can be combined into a physical map or a genetic map. The radiation hybrid technique begins as another way to amplify and purify DNA, th...
Wikipedia - Radiation reduced hybrid - Summary
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Section: Procedure. The procedure utilizes two cell lines, neither of which can survive in toxic media, but contain genes that can resist the toxin when contained by the same cell. The cell line under study is irradiated, causing breaks in the DNA. These cells are fused with the other cell line, producing a hybrid. If ...
Wikipedia - Radiation reduced hybrid - Procedure
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Article: Reading frame. In molecular biology, a reading frame is a specific choice out of the possible ways to read the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule as a sequence of triplets. Where these triplets equate to amino acids or stop signals during translation, they are called codons. A sing...
Wikipedia - Reading frame - Summary
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Section: Genetic code. DNA encodes protein sequence by a series of three-nucleotide codons. Any given sequence of DNA can therefore be read in six different ways: Three reading frames in one direction (starting at different nucleotides) and three in the opposite direction. During transcription, the RNA polymerase read ...
Wikipedia - Reading frame - Genetic code
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Section: Multiple reading frames. The usage of multiple reading frames leads to the possibility of overlapping genes; there may be many of these in viral, prokaryote, and mitochondrial genomes. Some viruses, e.g. hepatitis B virus and BYDV, use several overlapping genes in different reading frames. In rare cases, a rib...
Wikipedia - Reading frame - Multiple reading frames
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Section: Flu virus. The classical example of reassortment is seen in the 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 anim...
Wikipedia - Reassortment - Flu virus
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Article: Reciprocal silencing. Reciprocal silencing, a genetic phenomenon that primarily occurs in plants, refers to the pattern of redundant genes being silenced following a polyploid event. Polyploidy (wholesale genome duplication) is common in plants and constitutes an important method of speciation. When a polyploi...
Wikipedia - Reciprocal silencing - Summary
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Section: Reciprocal silencing between populations. Allopolyploids are species whose increased complement of genetic material is the result of hybridization of two closely related species. Thus homeologous chromosomes in allopolyploids are equivalent, but not identical. These differences mean that the precise pattern of...
Wikipedia - Reciprocal silencing - Reciprocal silencing between populations
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