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| 2. |
- Nordborg, M, et al.
(författare)
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The pattern of polymorphism in Arabidopsis thaliana
- 2005
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Ingår i: PLoS Biology. - : Public Library of Science (PLoS). - 1545-7885. ; 3:7, s. 1289-1299
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Tidskriftsartikel (refereegranskat)abstract
- We resequenced 876 short fragments in a sample of 96 individuals of Arabidopsis thaliana that included stock center accessions as well as a hierarchical sample from natural populations. Although A. thaliana is a selfing weed, the pattern of polymorphism in general agrees with what is expected for a widely distributed, sexually reproducing species. Linkage disequilibrium decays rapidly, within 50 kb. Variation is shared worldwide, although population structure and isolation by distance are evident. The data fail to fit standard neutral models in several ways. There is a genome-wide excess of rare alleles, at least partially due to selection. There is too much variation between genomic regions in the level of polymorphism. The local level of polymorphism is negatively correlated with gene density and positively correlated with segmental duplications. Because the data do not fit theoretical null distributions, attempts to infer natural selection from polymorphism data will require genome-wide surveys of polymorphism in order to identify anomalous regions. Despite this, our data support the utility of A. thaliana as a model for evolutionary functional genomics.
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- Jakobsson, Mattias, et al.
(författare)
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A unique recent origin of the allotetraploid species Arabidopsis suecica: Evidence from nuclear DNA markers
- 2006
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 23:6, s. 1217-1231
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Tidskriftsartikel (refereegranskat)abstract
- A coalescent-based method was used to investigate the origins of the allotetraploid Arabidopsis suecica, using 52 nuclear microsatellite loci typed in eight individuals of A. suecica and 14 individuals of its maternal parent Arabidopsis thaliana, and four short fragments of genomic DNA sequenced in a sample of four individuals of A. suecica and in both its parental species A. thaliana and Arabidopsis arenosa. All loci were variable in A. thaliana but only 24 of the 52 microsatellite loci and none of the four sequence fragments were variable in A. suecica. We explore a number of possible evolutionary scenarios for A. suecica and conclude that it is likely that A. suecica has a recent, unique origin between 12,000 and 300,000 years ago. The time estimates depend strongly on what is assumed about population growth and rates of mutation. When combined with what is known about the history of glaciations, our results suggest that A. suecica originated south of its present distribution in Sweden and Finland and then migrated north, perhaps in the wake of the retreating ice.
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| 4. |
- Mahanta, C., et al.
(författare)
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Source, distribution and release mechanisms of arsenic in the groundwater of Assam floodplains of Northeast India
- 2008
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Ingår i: World Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008. - Reston, VA : American Society of Civil Engineers. - 9780784409763
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Konferensbidrag (refereegranskat)abstract
- This study conducted in Bongaigaon and Darrang districts of Assam, India is based upon water chemistry and sediment characteristics investigation in an reportedly arsenic infested belt. Of total 50 sampled wells, 15 had arsenic concentration above national drinking water standard of 50 μg/l, and 33 had As concentrations above the WHO guideline of 10 μg/l. However no distinct zones or depths with specific sedimentological features could be identified. Sediments with colour on green-olive scale are probably more likely to bear As contaminated water than white sediments. Sand filters used to reduce high iron content seem to reduce As content of water effectively. Arsenic rich water is also partly avoided since drillers seek water low in iron, which is often also low in arsenic content. Reductive dissolution of Ferric hydroxides is believed to be the release mechanism controlling the mobility of arsenic, rather than oxidation of arsenopyrite or pH induced desorption.
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