gene pool

gene pool

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  Presented BY: PARUL
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  INTRODUCTION Gene pool complete setof unique alleles that would be found by inspecting the genetic material of every living member of that species or population.
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  Genetic pollution Genetic contamination orgenetic swamping happens when original set of naturally evolved (wild) region specific genes / gene pool of wild animals and plants become hybridized with the genes of other non-native wild species or subspecies from neighboring or far away regions.
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  Exotic Fish: Exotic fishis alien species which is not native and belonging by nature or origin to another part of the world or brought in from abroad or foreign Alteration/extinction of gene pools of the species/stocks by crossbreeding or hybridization & backcrossing.
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  Nature of introductions Intentionalintroductions • In the first case, organisms are purposely released for establishment in the wild. • If it is not initially successful, humans have made repeated introductions to improve the probability that the species will survive and eventually reproduce in the wild. • In these cases it is clear that the introduction is directly facilitated by human desires.
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  • In thesecond case, species intentionally transported into a new region may escape from captive or cultivated populations and subsequently establish independent breeding populations. • Escaped organisms are included in this category because their initial transport to a new region is human motivated.
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  Unintentional introductions/accidental • Increasingrates of human travel are providing accelerating opportunities for species to be accidentally transported into areas in which they are not considered native.
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  Introgression through Hybridization •One of the reasons for the increased frequency of hybridization is introduction of exotic species. • Hybridization may lead to hybrid vigor or heterosis due to over dominance and heterozygocity at many loci or may lead to genetic pollution. • Hybridization between an alien species and a native one leads to genetic introgression. This is the transmission of genes from one species to another through hybridization.
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  Extinction due toHybridization • Hybridization between exotic and native species has not only brought in genetic contamination but even resulted in species extinction in some cases. • Apache trout (Oncorhynchus apache) & Gila trout (O. gilae), two native species of Southwest USA, have faced extinction primarily due to hybridization with the introduced species, Cutthroat trout (O. clarkii) & O. mykiss.
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  Loss Of Traits •Loss of traits leading to economic value decline takes place in uncontrolled hybridization between exotic and native species. • Hybridization between Bighead (Aristichthys nobilis) & Silver carp (Hypophthalmichthys molitrix) showed beneficial properties in terms of growth, food conversion & disease resistance. • But in further uncontrolled hybridization of these fishes in later generation, the offspring lost the acquired beneficial traits.
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  Genetic Bottleneck • Agenetic bottleneck is the sudden and drastic decline in numbers. It effectively samples a few individuals from a larger gene pool, resulting in a remnant population with less overall variation. • Loss of variation has two components like reduction in variance of qualitative traits and loss of specific and usually rare alleles.
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  EXAMPLES • The introductionof rainbow trout in some Tien Shan lakes initially resulted in spectacular growth rates, but within several generations the growth rate slowed down, fecundity of females declined, and eventually cannibalism took place. Coregonids (six species) introduced into lakes in northeastern Kazakhstan with the purpose of increasing commercial catches also showed a decline in growth rates.
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  REFERENCES:  Role ofexotic species in aquaculture: problems and prospects in Indochina Amararatne Yakupitiyage and Ram C. Bhujel  Gene flow in the environment –genetic pollution? G.R. Squire, N. Augustin, J. Bown1, J.W. Crawford, G. Dunlop, J. Graham, J.R. Hillman, B. Marshall, D. Marshall, G. Ramsay, D.J. Robinson, J. Russell, C. Thompson & G. Wright. Wikipedia What is genetic pollution? Published on NW Resistance Against Genetic Engineering (http://nwrage.org)