Differences among clones are tiny, and genetic uniformity makes crop failure a serious risk to the global rubber supply.
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The ants' unusual mix of genetic uniformity and wildly protean conduct offers a powerful tool for cracking the old nature-versus-nurture conundrum, and the Kronauer researchers have been mapping out the interplay between genes and environmental cues in shaping essential behaviors like reproduction and sociality.
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Transactions of the British Mycological Society, 63(OCT): 391-393. Since this pathogen affects trees, orchards are very susceptible to infection due to the genetic uniformity of the plants therein.Slippers, B., G. Fourie, P.W. Crous, T.A. Coutinho, B.D. Wingfield, A.J. Carnegie and M.J. Wingfield, 2004. Speciation and distribution of botryosphaeria spp.
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J. Bot. 37; 1101-1130. This system of locking cannot function in a crop pathosystem in which the host population has genetic uniformity. A crop pathosystem is usually the equivalent of every door in the town having the same lock, and every householder having the same key which fits every lock.
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This was due to the return usage of normal cytoplasm corn, not as conducive weather, residues being buried, and planting early. The SCLB epidemic highlighted the issue of genetic uniformity in monoculture crops, which allows for a greater likelihood of new pathogen races and host vulnerability. In the present day, there are many management methods and better education practices but the disease can still be an issue in tropical climates, causing devastating yield losses up to 70%.
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This is in contrast to what humans share in the "unusually high level of genetic uniformity in the human species" (compared to for example, chimpanzee subspecies). Scholars speculate about the evolutionary purpose of such differentiation served; it may have contributed to group solidarity when social groups were small tribes of hunter gatherers, lived further apart in different regions, and were divided by many cultural factors. He suggests that such differentiation may be an "information-rich way to classify people".
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In most animals the embryo is the sessile initial stage of the individual life cycle, and is followed by the emergence (that is, the hatching) of a motile stage. The zygote or the ovum itself or the sessile organic vessel containing the developing embryo may be called the egg. A recent proposal suggests that the phylotypic animal body plans originated in cell aggregates before the existence of an egg stage of development. Eggs, in this view, were later evolutionary innovations, selected for their role in ensuring genetic uniformity among the cells of incipient multicellular organisms.
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Since P. spyrothecae clonally reproduce, genetic relatedness within colonies is rather simple: an individual aphid is either a clone of its neighbors or it is not. Since every generation within the gall displays a high degree of relatedness due to cloning, any deviation from a colony's genetic uniformity (excluding mutation) can be traced back to intergall migration. The ease of intergall migration is rooted in the fact that the colonies are present in the galls on the primary host for a long period of time, only migrating once the summer has passed.
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Del Tredici also studied the ginkgo (Ginkgo biloba) for decades. He was part of a 1989 expedition that found wild ginkgos in Tian Mu Shan Reserve, a notable find since this species had been long believed extinct in the wild.It is not undisputed that these are truly wild, as the population shows a relative genetic uniformity that could indicate that they were planted and preserved by Chinese monks over a long period (See ), but later research by Wei Gong has indicated that the find likely was of wild trees. He demonstrated that gingko basal lignotubers develop from suppressed cotyledonary (embryonic leaf) buds – a resprouting mechanism activated under stress that, according to Del Tredici, helps explain the gingko's long survival as a species.
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The Hardy–Weinberg principle states that within sufficiently large populations, the allele frequencies remain constant from one generation to the next unless the equilibrium is disturbed by migration, genetic mutations, or selection. However, in finite populations, no new alleles are gained from the random sampling of alleles passed to the next generation, but the sampling can cause an existing allele to disappear. Because random sampling can remove, but not replace, an allele, and because random declines or increases in allele frequency influence expected allele distributions for the next generation, genetic drift drives a population towards genetic uniformity over time. When an allele reaches a frequency of 1 (100%) it is said to be "fixed" in the population and when an allele reaches a frequency of 0 (0%) it is lost.
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Although Ginkgo biloba and other species of the genus were once widespread throughout the world, its range shrank and by two million years ago, it was restricted to a small area of China. For centuries, it was thought to be extinct in the wild, but is now known to grow in at least two small areas in Zhejiang province in eastern China, in the Tianmushan Reserve. However, high genetic uniformity exists among ginkgo trees from these areas, arguing against a natural origin of these populations and suggesting the ginkgo trees in these areas may have been planted and preserved by Chinese monks over a period of about 1,000 years. This study demonstrates a greater genetic diversity in Southwestern China populations, supporting glacial refugia in mountains surrounding eastern Tibetan Plateau, where several old- growth candidates for wild populations have been reported.
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Despite the evident diversity displayed by the world's distinctive Jewish populations, both culturally and physically, genetic studies have demonstrated most of these to be genetically related to one another, having ultimately originated from a common ancient Israelite population that underwent geographic branching and subsequent independent evolutions. A study published by the National Academy of Sciences stated that "The results support the hypothesis that the paternal gene pools of Jewish communities from Europe, North Africa, and the Middle East descended from a common Middle Eastern ancestral population, and suggest that most Jewish communities have remained relatively isolated from neighboring non- Jewish communities during and after the Diaspora." Researchers expressed surprise at the remarkable genetic uniformity they found among modern Jews, no matter where the diaspora has become dispersed around the world. Moreover, DNA tests have demonstrated substantially less inter-marriage in most of the various Jewish ethnic divisions over the last 3,000 years than in other populations.
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