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Polygenetic Shield Volcanoes
Polygenesis can refer to: * Polygenesis (linguistics), a theory of language origin * Polygenism, an obsolete theory of human origin * Gene duplication Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene ..., a form of genetic disorder resulting in the overexpression of a particular gene * Polygenetic landforms, landforms formed the accumulative action of various processes See also * Polygene, member of a group of interacting genes * Monogenism (other) {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polygenesis (linguistics)
In historical or evolutionary linguistics, monogenesis and polygenesis are two different hypotheses about the phylogenetic origin of human languages. According to monogenesis, human language arose only once in a single community, and all current languages come from the first original tongue. On the other hand, according to polygenesis, human languages came into being in several communities independently, and current tongues derived from different sources. Monogenesis The monogenetic theory points to a single origin of all of the world's languages and it is the most accepted theory. It states that all current languages have formed through language change from a single tongue that gradually differentiated into unintelligible languages. The first scholar to publish this theory was Alfredo Trombetti, in the book ''L'Unità d'origine del linguaggio'', published in 1905. More recently, Joseph Greenberg and Merritt Ruhlen, proponents of monogenesis, argue that in modern languages there ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polygenism
Polygenism is a theory of human origins which posits the view that humans are of different origins (polygenesis). This view is opposite to the idea of monogenism, which posits a single origin of humanity. Modern scientific views find little merit in any polygenic model due to an increased understanding of speciation in a human context, with the monogenic "Out of Africa" hypothesis and its variants being the most widely accepted models for human origins. Polygenism has historically been heavily used in service of white supremacist ideas and practices, denying a common origin between European and non-European peoples. It can be distinguished between Biblical polygenism, describing a Pre-Adamite or Co-Adamite origin of certain races in the context of the Genesis narrative of Adam and Eve, and scientific polygenism, attempting to find a taxonomic basis for ideas of racial science. Origins Many oral traditions feature polygenesis in their creation stories. For example, Bambuti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. Gene duplications can arise as products of several types of errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements. Common sources of gene duplications include ectopic recombination, retrotransposition event, aneuploidy, polyploidy, and replication slippage. Mechanisms of duplication Ectopic recombination Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The chance of it happening is a function of the degree of sharing of repetitive elements between two chromosomes. The products of this recombination are a duplication at the site of the exchange and a reciprocal deletion. Ectopic recombina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landform
A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, mountains, canyons, and valleys, as well as shoreline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great oceanic basins. Physical characteristics Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, structure stratification, rock exposure, and soil type. Gross physical features or landforms include intuitive elements such as berms, cliffs, hills, mounds, peninsulas, ridges, rivers, valleys, volcanoes, and numerous other structural and size-scaled (e.g. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polygene
A polygene is a member of a group of non- epistatic genes that interact additively to influence a phenotypic trait, thus contributing to multiple-gene inheritance (polygenic inheritance, multigenic inheritance, quantitative inheritance), a type of non-Mendelian inheritance, as opposed to single-gene inheritance, which is the core notion of Mendelian inheritance. The term "monozygous" is usually used to refer to a hypothetical gene as it is often difficult to distinguish the effect of an individual gene from the effects of other genes and the environment on a particular phenotype. Advances in statistical methodology and high throughput sequencing are, however, allowing researchers to locate candidate genes for the trait. In the case that such a gene is identified, it is referred to as a quantitative trait locus (QTL). These genes are generally pleiotropic as well. The genes that contribute to type 2 diabetes are thought to be mostly polygenes. In July 2016, scientists reported iden ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
