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Introgression
Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introgression is a long-term process, even when artificial; it may take many hybrid generations before significant backcrossing occurs. This process is distinct from most forms of gene flow in that it occurs between two populations of different species, rather than two populations of the same species. Introgression also differs from simple hybridization. Simple hybridization results in a relatively even mixture; gene and allele frequencies in the first generation will be a uniform mix of two parental species, such as that observed in mules. Introgression, on the other hand, results in a complex, highly variable mixture of genes, and may only involve a minimal percentage of the donor genome. Definition Introgression or introgressive hybridi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denisovan
The Denisovans or Denisova hominins ) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic. Denisovans are known from few physical remains and consequently, most of what is known about them comes from DNA evidence. No formal species name has been established pending more complete fossil material. The first identification of a Denisovan individual occurred in 2010, based on mitochondrial DNA (mtDNA) extracted from a juvenile female finger bone excavated from the Siberian Denisova Cave in the Altai Mountains in 2008. Nuclear DNA indicates close affinities with Neanderthals. The cave was also periodically inhabited by Neanderthals, but it is unclear whether Neanderthals and Denisovans ever cohabited in the cave. Additional specimens from Denisova Cave were subsequently identified, as was a single specimen from the Baishiya Karst Cave on the Tibetan Plateau. DNA evidence suggests they had dark skin, eyes, and hair, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neanderthal
Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the "causes of Neanderthal disappearance about 40,000 years ago remain highly contested," demographic factors such as small population size, inbreeding and genetic drift, are considered probable factors. Other scholars have proposed competitive replacement, assimilation into the modern human genome (bred into extinction), great climate change, climatic change, disease, or a combination of these factors. It is unclear when the line of Neanderthals split from that of Early modern human, modern humans; studies have produced various intervals ranging from 315,000 to more than 800,000 years ago. The date of divergence of Neanderthals from their ancestor ''Homo heidelbergensis, H. heidelbergensis'' is also unclear. The oldest potential ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interspecific Hybrid
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in blending inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridisation, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Flow
In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybridization (biology)
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in blending inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridisation, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid (biology)
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in blending inheritance), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridisation, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hybrid Zone
A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. Hybrid zones can form ''in situ'' due to the evolution of a new lineage but generally they result from secondary contact of the parental forms after a period of geographic isolation, which allowed their differentiation (or speciation). Hybrid zones are useful in studying the genetics of speciation as they can provide natural examples of differentiation and (sometimes) gene flow between populations that are at some point between representing a single species and representing multiple species in reproductive isolation. Definition Hybrid zones are areas where the hybrid offspring of two divergent taxa (species, subspecies or genetic "forms") are prevalent and there is a cline in the genetic composition of populations from one taxon to the other. The two (or more) genetically differentiated species or lineages contributing to formation of a hybrid zone are r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mallard
The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Argentina, Chile, Colombia, the Falkland Islands, and South Africa. This duck belongs to the subfamily Anatinae of the waterfowl family Anatidae. Males have purple patches on their wings, while the females (hens or ducks) have mainly brown-speckled plumage. Both sexes have an area of white-bordered black or iridescent blue feathers called a speculum on their wings; males especially tend to have blue speculum feathers. The mallard is long, of which the body makes up around two-thirds the length. The wingspan is and the bill is long. It is often slightly heavier than most other dabbling ducks, weighing . Mallards live in wetlands, eat water plants and small animals, and are social animals preferring to congregate in groups or flocks of varyin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Black Duck
The Pacific black duck (''Anas superciliosa''), commonly known as the PBD, is a dabbling duck found in much of Indonesia, New Guinea, Australia, New Zealand, and many islands in the southwestern Pacific, reaching to the Caroline Islands in the north and French Polynesia in the east. It is usually called the gray duck in New Zealand, where it is also known by its Maori name, . Taxonomy The Pacific black duck was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's ''Systema Naturae''. He placed it with all the other ducks, geese and swans in the genus ''Anas'' and coined the binomial name ''Anas superciliosa''. Gmelin based his description on the "Supercilious duck" that had been described in 1785 by the English ornithologist John Latham in his ''A General Synopsis of Birds''. The naturalist Joseph Banks had provided Latham with a water-colour drawing of the duck by Georg Forster who had accompanied Jam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feral Cat
A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact: it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens of generations and become an aggressive local apex predator in urban, savannah and bushland environments. Some feral cats may become more comfortable with people who regularly feed them, but even with long-term attempts at socialization, they usually remain aloof and are most active after dusk. Feral cats are devastating to wildlife, and conservation biologists consider them to be one of the worst invasive species on Earth. Attempts to control feral cat populations are widespread but generally of greatest impact within purpose-fenced reserves. Some animal rights groups advocate trap-neuter-return programs to prevent the feral cats from continuing to breed. Scientific evidence has demonstrated that TNR is not effective at controlling ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canid Hybrid
Canid hybrids are the result of interbreeding between the species of the genus '' Canis''. This often occurs in the wild, and in particular between domestic or feral dogs with wild native canids. Genetic considerations The wolf-like canids are a group of large carnivores that are genetically closely related because they all possess 78 chromosomes, arranged in 39 pairs and are karyologically indistinguishable from each other. The group includes the genera ''Canis'', ''Cuon'', ''Lupulella'' and ''Lycaon''. The members are the domestic dog ''(C. familiaris)'', gray wolf (''C. lupus''), dingo (''C. lupus dingo''), coyote (''C. latrans''), golden jackal (''C. aureus''), African wolf (''C. lupaster''), Ethiopian wolf (''C. simensis''), dhole (''Cuon alpinus''), black-backed jackal (''Lupulella mesomelas''), side-striped jackal (''L. adusta'') and African wild dog (''Lycaon pictus''). Newly proposed members include the red wolf (''Canis rufus''), and the eastern wolf (''Canis lycao ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backcrossing
Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, to achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and production of gene knockout organisms. Backcrossed hybrids are sometimes described with acronym "BC"; for example, an F1 hybrid crossed with one of its parents (or a genetically similar individual) can be termed a BC1 hybrid, and a further cross of the BC1 hybrid to the same parent (or a genetically similar individual) produces a BC2 hybrid. Plants Advantages * If the recurrent parent is an elite genotype, at the end of the backcrossing programme, an elite genotype is recovered. * As no "new" recombination results, the elite combination is not lost. Disadvantages * It works poorly for quantitative traits. * It is more restricted for recessive traits. * In practice, sections of genome from the nonrecurrent parents are often still presen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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