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QST (genetics)
In quantitative genetics, QST is a statistic intended to measure the degree of genetic differentiation among populations with regard to a quantitative trait. It was developed by Ken Spitze in 1993. Its name reflects that QST was intended to be analogous to the fixation index for a single genetic locus (FST). QST is often compared with FST of neutral loci to test if variation in a quantitative trait is a result of divergent selection or genetic drift, an analysis known as QST–FST comparisons. Calculation of QST Equations QST represents the proportion of variance among subpopulations, and its calculation is synonymous to FST developed by Sewall Wright. However, instead of using genetic differentiation, QST is calculated by finding the variance of a quantitative trait within and among subpopulations, and for the total population. Variance of a quantitative trait among populations (σ2GB) is described as: \sigma_^2 = (1-Q_)\sigma_T^2 And the variance of a quantitative trait wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantitative Genetics
Quantitative genetics deals with phenotypes that vary continuously (such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical). Both branches use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes only summaries of the underlying genetics. Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the ''effect size'', the ''mean'' and the ''variance'') to link phenotypes (attributes) to genotypes. Some phenotypes may be analyzed either as discrete categories or as continuo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type I And Type II Errors
In statistical hypothesis testing, a type I error is the mistaken rejection of an actually true null hypothesis (also known as a "false positive" finding or conclusion; example: "an innocent person is convicted"), while a type II error is the failure to reject a null hypothesis that is actually false (also known as a "false negative" finding or conclusion; example: "a guilty person is not convicted"). Much of statistical theory revolves around the minimization of one or both of these errors, though the complete elimination of either is a statistical impossibility if the outcome is not determined by a known, observable causal process. By selecting a low threshold (cut-off) value and modifying the alpha (α) level, the quality of the hypothesis test can be increased. The knowledge of type I errors and type II errors is widely used in medical science, biometrics and computer science. Intuitively, type I errors can be thought of as errors of ''commission'', i.e. the researcher unlu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Diversity
Genetic diversity is the total number of Genetics, genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is distinguished from ''genetic variability'', which describes the tendency of genetic characteristics to vary. Genetic diversity serves as a way for populations to adapt to changing environments. With more variation, it is more likely that some individuals in a population will possess variations of alleles that are suited for the environment. Those individuals are more likely to survive to produce offspring bearing that allele. The population will continue for more generations because of the success of these individuals. The academic field of population genetics includes several hypotheses and theories regarding genetic diversity. The neutral theory of evolution proposes that diversity is the result of the accumulation of neutral subs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Divergent Evolution
Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to speciation. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that drive adaptations to their new environment. After many generations and continual evolution, the populations become less able to interbreed with one another. The American naturalist J. T. Gulick (1832–1923) was the first to use the term "divergent evolution", with its use becoming widespread in modern evolutionary literature. Classic examples of divergence in nature are the adaptive radiation of the finches of the Galapagos or the coloration differences in populations of a species that live in different habitats such as with pocket mice and fence lizards. The term can also be applied in molecular evolution, such as to pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conservation Genetics
Conservation genetics is an interdisciplinary subfield of population genetics that aims to understand the dynamics of genes in populations principally to avoid extinction. Therefore, it applies genetic methods to the conservation and restoration of biodiversity. Researchers involved in conservation genetics come from a variety of fields including population genetics, molecular ecology, biology, evolutionary biology, and systematics. Genetic diversity is one of the three fundamental levels of biodiversity, so it is directly important in conservation. Genetic variability influences both the health and long-term survival of populations because decreased genetic diversity has been associated with reduced fitness, such as high juvenile mortality, diminished population growth, reduced immunity, and ultimately, higher extinction risk. Genetic diversity Genetic diversity is the variability of genes in a species. A number of means can express the level of genetic diversity: observed he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantitative Genetics
Quantitative genetics deals with phenotypes that vary continuously (such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical). Both branches use the frequencies of different alleles of a gene in breeding populations (gamodemes), and combine them with concepts from simple Mendelian inheritance to analyze inheritance patterns across generations and descendant lines. While population genetics can focus on particular genes and their subsequent metabolic products, quantitative genetics focuses more on the outward phenotypes, and makes only summaries of the underlying genetics. Due to the continuous distribution of phenotypic values, quantitative genetics must employ many other statistical methods (such as the ''effect size'', the ''mean'' and the ''variance'') to link phenotypes (attributes) to genotypes. Some phenotypes may be analyzed either as discrete categories or as continuo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F-statistics
In population genetics, ''F''-statistics (also known as fixation indices) describe the statistically expected level of heterozygosity in a population; more specifically the expected degree of (usually) a reduction in heterozygosity when compared to Hardy–Weinberg expectation. ''F''-statistics can also be thought of as a measure of the correlation between genes drawn at different levels of a (hierarchically) subdivided population. This correlation is influenced by several evolutionary processes, such as genetic drift, founder effect, bottleneck, genetic hitchhiking, meiotic drive, mutation, gene flow, inbreeding, natural selection, or the Wahlund effect, but it was originally designed to measure the amount of allelic fixation owing to genetic drift. The concept of ''F''-statistics was developed during the 1920s by the American geneticist Sewall Wright, who was interested in inbreeding in cattle. However, because complete dominance causes the phenotypes of homozygote domi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all species have subspecies, but for those that do there must be at least two. Subspecies is abbreviated subsp. or ssp. and the singular and plural forms are the same ("the subspecies is" or "the subspecies are"). In zoology, under the International Code of Zoological Nomenclature, the subspecies is the only taxonomic rank below that of species that can receive a name. In botany and mycology, under the International Code of Nomenclature for algae, fungi, and plants, other infraspecific ranks, such as variety, may be named. In bacteriology and virology, under standard bacterial nomenclature and virus nomenclature, there are recommendations but not strict requirements for recognizing other important infraspecific ranks. A taxonomist decides w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antirrhinum Majus
''Antirrhinum majus'', the common snapdragon (often - especially in horticulture - simply "snapdragon"), is a species of flowering plant belonging to the genus '' Antirrhinum''. The plant was placed in the family Plantaginaceae following a revision of its prior classical family, Scrophulariaceae. The common name "snapdragon", originates from the flowers' reaction to having their throats squeezed, which causes the "mouth" of the flower to snap open like a dragon's mouth. It is widely used as an ornamental plant in borders and as a cut flower. It is perennial but usually cultivated as an annual plant. The species has been in culture since the 15th century. Taxonomy There are five subspecies: *''Antirrhinum majus'' subsp. ''majus''. Southern France, northeast Spain. *''Antirrhinum majus'' subsp. ''cirrhigerum'' (Ficalho) Franco. Southern Portugal, southwest Spain. *''Antirrhinum majus'' subsp. ''linkianum'' (Boiss. & Reut.) Rothm. Western Portugal (endemic). *''Antirrhinum ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colonisation (biology)
Colonisation or colonization is the process in biology by which a species spreads to new areas. Colonisation often refers to ''successful'' immigration where a population becomes integrated into an ecological community, having resisted initial local extinction. In ecology, it is represented by the symbol ''λ'' (lowercase lambda) to denote the long-term intrinsic growth rate of a population. One classic scientific model in biogeography posits that species must continue to colonize new areas through its life cycle (called a ''taxon cycle'') in order to achieve longevity. Accordingly, colonisation and extinction are key components of island biogeography, a theory that has many applications in ecology, such as metapopulations. Scale Colonisation occurs on several scales. In the most basic form, as biofilm in the formation of communities of microorganisms on surfaces. In small scales such as colonising new sites, perhaps as a result of environmental change. And on larger s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachypodium Sylvaticum
''Brachypodium sylvaticum'', commonly known as false-brome, slender false brome or wood false brome, is a perennial grass native to Europe, Asia and Africa. It has a broad native range stretching from North Africa to Eurasia. The bunchgrass is most commonly found in forests and woodlands, preferring the shaded canopy, but may grow in open areas. It prefers well drained neutral and calcerous soils, and avoids wet conditions. Description ''Brachypodium sylvaticum'' is a tall tufted perennial bunchgrass that grows up to about a high. The drooping leaf blade of the plant is dark green, or bright-yellow green, flat and up to 12 mm wide with a fringe of hairs surrounding the edge of the leaf. The leaves do not have auricles. The leaf blade is joined to the hollow culm by the leaf sheath. This hairy sheath is open and surrounds the culm. The culm is pilose (long, soft, hairy), and typically has 4 to 5 nodes. The ligules are blunt, long. The grass has drooping narro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinus Albicaulis
''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a conifer tree native to the mountains of the western United States and Canada, specifically subalpine areas of the Sierra Nevada, Cascade Range, Pacific Coast Ranges, and Rocky Mountains. It shares the common name "creeping pine" with several other plants. The whitebark pine is typically the highest-elevation pine tree found in these mountain ranges and often marks the tree line. Thus, it is often found as ''krummholz'', trees growing close to the ground that have been dwarfed by exposure. In more favorable conditions, the trees may grow to in height. Identification Whitebark pine is a member of the white pine group, the ''Pinus'' subgenus ''Strobus'', and the section ''Strobus''; like all members of this group, the leaves (needles) are in fascicles (bundles) of five with a deciduous sheath. This distinguishes whitebark pine and its r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
