Search results for "VARIATION"
showing 10 items of 2124 documents
Natural Genetic Variation of Freezing Tolerance in Arabidopsis
2006
Abstract Low temperature is a primary determinant of plant growth and survival. Using accessions of Arabidopsis (Arabidopsis thaliana) originating from Scandinavia to the Cape Verde Islands, we show that freezing tolerance of natural accessions correlates with habitat winter temperatures, identifying low temperature as an important selective pressure for Arabidopsis. Combined metabolite and transcript profiling show that during cold exposure, global changes of transcripts, but not of metabolites, correlate with the ability of Arabidopsis to cold acclimate. There are, however, metabolites and transcripts, including several transcription factors, that correlate with freezing tolerance, indica…
Intra-allelic variation in introns of the S13-RNase allele distinguishes sweet, wild and sour cherries
2010
The cherry (Prunus avium), a self-incompatible diploid species, and the sour cherry (Prunus cerasus), a self-incompatible or self-compatible allotetraploid species derived from P. avium and Prunus fruticosa, share several S-RNase alleles, including S13. An inactive form, S13° ,i s found in some sour cherries. Two (AT) microsatellites are associated with allele S13-RNase, one in the first intron and one in the second. Their length polymorphisms were studied in 14 sweet and 17 wild cherries (both P. avium) and in 42 sour cherries. Fluorescent primers amplifying each microsatellite were designed and amplification prod- ucts sized on an automated sequencer. Variants ranged from 247 to 273 bp fo…
Allozymic variation in Mediterranean hake, Merluccius merluccius (Gadidae)
1998
Abstract Four hundred and twenty individual hake from 10 sample sites in the Mediterranean Sea were analysed in order to study genetic variability and identify genetic stock structure. Twenty loci were identified, four of which were polymorphic at the 95% level: ADH*, PGI‐1*, PGI‐2* and SOD‐1*. Average observed and expected heterozygosity were 0.084 and 0.090, respectively. PG1–1* deviated from Hardy‐Weinberg expectations due to an excess of heterozygotes and F‐statistic analysis showed also a significant excess of heterozygosity at SOD‐1*. FST was not significant for each locus except for PGI‐2*, where a single sample from the Channel of Sicily (C5) showed a different pattern in allelic fr…
Impacto de la apolipoproteína A5 en el riesgo cardiovascular: Modulaciones genéticas y ambientales
2010
Triglyceride concentrations are an independent risk factor for coronary heart disease. Apolipoprotein A5 gene (APOA5) has an important role determining triglyceride metabolism and it is a potential cardiovascular risk. However the mechanisms for these actions are not well-known. Despite the different allelic frequency of its major polymorphisms in different populations, multiple studies have shown consistent associations between these variants and fasting triglycerides. Variations in the APOA5 gene have also been associated with postprandial triglycerides, as well as with different sizes of lipoproteins and other markers. Moreover, some of the APOA5 gene variants have been associated with i…
Epidemic dynamics of two coexisting hepatitis C virus subtypes.
2006
Hepatitis C virus (HCV) infection affects about 3 % of the human population. Phylogenetic analyses have grouped its variants into six major genotypes, which have a star-like distribution and several minor subtypes. The most abundant genotype in Europe is the so-called genotype 1, with two prevalent subtypes, 1a and 1b. In order to explain the higher prevalence of subtype 1b over 1a, a large-scale sequence analysis (100 virus clones) has been carried out over 25 patients of both subtypes in two regions of the HCV genome: one comprising hypervariable region 1 and another including the interferon sensitivity-determining region. Neither polymorphism analysis nor molecular variance analysis (att…
Isolation and use of microsatellite loci in Melicertus kerathurus (Crustacea, Penaeidae).
2010
Melicertus kerathurus represents an economically important resource for fisheries and aquaculture. Seven microsatellite loci from 373 specimens of M. kerathurus collected in different parts of the Mediterranean and NE Atlantic were identified. Four of these microsatellites showed a moderate level of polymorphism, with 2 to 14 alleles per locus, whereas three had a monomorphic profile. Observed and expected heterozygosity ranged between 0.28 to0.64 and 0.28 to 0.65, respectively. Three microsatellite loci deviated from Hardy-Weinberg equilibrium in some populations, with a deficit of heterozygosity. Mean Fst values showed significant differentiation among sample sites analysed and indicate t…
Genetic differentiation in the striped dolphin Stenella coeruleoalba from European waters according to mitochondrial DNA (mtDNA) restriction analysis
1999
We used mitochondrial DNA (mtDNA) restriction analysis to study genetic variation in 98 striped dolphins (Stenella coeruleoalba) stranded on coasts from different European countries and from animals caught by fisheries. A total of 63 different restriction sites was mapped after digestion of mtDNA with 15 restriction endonucleases that yielded a total of 27 haplotypes. No haplotype was shared between Mediterranean and Atlantic areas. All the analyses indicate the existence of two different populations with a very limited gene flow across the Strait of Gibraltar.
Sampling and repeatability in the evaluation of hepatitis C virus genetic variability.
2003
Among the experimental techniques available to study the genetic variability of RNA virus populations, the most informative involve reverse transcription (RT), amplification, cloning and sequencing. The effects of several aspects of these techniques on the estimation of genetic variability in a virus population were analysed. Hepatitis C virus populations from four patients were examined. For each patient, ten series of data derived from independent PCR amplifications of a single RT reaction were obtained. The sample size of each data set was 10 sequences (in nine series) and 100 sequences (in one series). An additional data set derived from an independent RT reaction (about 10 sequences) p…
A hierarchical analysis of genetic structure and variability in patchily distributed coexisting Chiastocheta species (Diptera:Anthomyiidae)
1996
The pattern of genetic variation in four coexisting fly species of the genus Chiastocheta was studied by allozyme electrophoresis. The fly species are confined to patches of one plant, Trollius europaeus, and thus experience very similar habitat fluctuations. Collection sites were chosen in a hierarchical fashion and F-statistics were estimated at three levels: intraregion, inter-region and total population. Population characteristic genetic parameters were compared within and among species and were related to the hierarchical level. The species were used as replicate experiments for inference of habitat history, and the hierarchical levels were used as inference for specific gene flow patt…
Genetic basis of trichome production in Arabidopsis lyrata.
2002
Leaf trichomes may protect plants against herbivorous insects, and may increase tolerance to drought and UV-radiation. The perennial herb Arabidopsis lyrata (Brassicaceae) is polymorphic for trichome production and occurs in a glabrous and trichome-producing form. In addition, there is quantitative variation in trichome density among trichome-producing plants. To examine the genetic basis of glabrousness, we conducted controlled crosses with plants originating from two natural populations in Sweden (one polymorphic for trichome-production, and one consisting of glabrous plants only). In addition, we estimated the heritability of trichome number from parent-offspring regressions for plants o…