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201.
202.
Evolution of SINE S1 retroposons in Cruciferae plant species 总被引:3,自引:0,他引:3
Lenoir A; Cournoyer B; Warwick S; Picard G; Deragon JM 《Molecular biology and evolution》1997,14(9):934-941
The S1 element is a plant short interspersed element (SINE) that was first
described and studied in Brassica napus. In this work, we investigated the
distribution and the molecular phylogeny of the S1 element within the
Cruciferae (= Brassicaceae). S1 elements were found to be widely
distributed within the Cruciferae, especially in species of the tribe
Brassiceae. The molecular phylogeny of S1 elements in eight Cruciferae
species (Brassica oleracea, Brassica rapa, Brassica napus, Brassica nigra,
Sinapis, arvensis, Sinapis pubescens, Coincya monensis, and Vella spinosa)
was inferred using 14-36 elements per species. Significant neighbor-joining
and maximum-parsimony phylogenetic clusters, supported by high bootstrap P
values and/or represented in 100% of the most-parsimonious trees, were
observed for each species. Most of these clusters probably correspond to
recent species-specific bursts of S1 amplification. Since these species
diverged recently, S1 amplification in Cruciferae plants is proposed to be
a highly dynamic process that could contribute to genome rearrangements and
eventually lead to reproductive isolation. S1 sequence analysis also
revealed putative gene conversion events that occurred between different S1
elements of a given species. These events suggest that gene conversion is a
minor but significant component of the molecular drive governing S1
concerted evolution.
相似文献
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206.
Size homoplasy and mutational processes of interrupted microsatellites in two bee species, Apis mellifera and Bombus terrestris (Apidae) 总被引:6,自引:0,他引:6
Similar microsatellite electromorphs (PCR products of the same size) can
arise from independent mutational events. Such alleles are not identical by
descent. This phenomenon, termed size homoplasy, was studied by sequencing
electromorphs of two microsatellite loci in which the stretch of basic
repeats is interrupted by different short (1-2 bp) DNA motifs. The number
and position of these interruptions were established for electromorphs from
closely and distantly related populations of honeybees and bumblebees. No
sequence difference was found when electromorphs came from the same
subspecies or from closely related subspecies, suggesting that they were
probably identical by descent. In contrast, sequence differences were often
detected in distantly related subspecies, showing that size homoplasy
frequently occurs at this level of population differentiation. Size
homoplasy is increased by limits to free length variation of alleles, a
phenomenon that seems to act on interrupted microsatellites when comparing
distantly related taxa, that is, honeybee subspecies from different
evolutionary lineages. Electromorph sequences suggest that, within the
scope of these limits, large mutation events have occurred frequently at
both interrupted loci studied. In good agreement with the molecular data,
computations based on the observed heterozygosity and number of
electromorphs and simulation studies showed that neither locus fits the
one-step stepwise mutant model (SMM). We speculate that interrupted
microsatellites in general could be characterized by a higher variance in
repeat number and consequently a lower homoplasy rate than pure ones.
Hence, interrupted microsatellites should be most appropriate for
investigating population differentiation and evolutionary relationship
between relatively distant populations.
相似文献
207.
Roel GW Verhaak Frank JT Staal Peter JM Valk Bob Lowenberg Marcel JT Reinders Dick de Ridder 《BMC bioinformatics》2006,7(1):105-15
Background
Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers. 相似文献208.
Background
Application of phenetic methods to gene expression analysis proved to be a successful approach. Visualizing the results in a 3-dimentional space may further enhance these techniques. 相似文献209.
210.