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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 38 (1994), S. 188-203 
    ISSN: 1432-1432
    Keywords: FASTA ; Similarities ; Introns ; Exons ; Motifs ; Leucine zipper ; DNA binding regions ; Distant resemblances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When investigators undertake searches of DNA databases, they normally discard large numbers of alignments that demonstrate very weak resemblances to each other, retaining only those that show statistically significant levels of resemblance. We show here that a great deal of information can be extracted from these weak alignments by examining them en masse. This is done by building three-dimensional similarity landscapes from the alignments, landscapes that reveal whether an unusual number of individually nonsignificant alignments tend to match up to a particular region of the query sequence being searched. The power of the search is increased by the use of libraries consisting entirely of introns or of exons. We show that (1) similarity landscapes with a variety of features can be generated from both intron and exon libraries, using introns or exons as query sequences; (2) the landscape features are real and not a statistical artifact; (3) well-known protein motifs used as query sequences can generate various landscape features; and (4) there is some evidence for resemblances between short regions of sequence carried by introns and exons. One possible interpretation of these results is that both introns and exons may have been built up during their evolution from short regions of sequence that as a result are now widely distributed throughout eukaryotic genomes. Such an interpretation would imply that these short regions have common ancestry. Alternatively, the wide sharing of short pieces of DNA may reflect regions with particular structural properties that have arisen through convergent evolution. The similarity-landscape approach can be used to detect such widespread structural motifs and sequence motifs in the genome that might be missed by less-global searches. It can also be used in conjunction with algorithms developed for detecting significant multiple alignments by isolating promising subsets of the databases that can be examined in more detail.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 15 (1996), S. 0 
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract We describe the identification of polymorphic microsatellite loci in the pathogenic yeast, Candida albicans. A search for all coding-region microsatellites with more than four repeats that can be found in Candida sequences in GenBank was conducted. Nine such microsatellite sequences consisting of trinucleotide motifs were found. Three of these were perfect microsatellites while the remaining six sequences were found in one imperfect microsatellite and two compound microsatellites. Because of the close proximity of some of these repeats, all could be assayed with six PCR primer pairs. All of these microsatellite sequences were found in five nuclear genes, ZNF1, CCN1, CPH1, EFG1, and MNT2. Except for a single (CTT)5 serine tract, all coded for polyglutamine tracts. Another locus with seven alleles, a region of the ERK1 protein kinase gene, was also examined, and may be a representative of a new class of highly polymorphic ‘clustered’ microsatellites. Such loci, in which several non-contiguous but closely linked microsatellites are clustered together, may be a useful source of DNA polymorphisms in microorganisms in which long microsatellite sequences are unavailable. All seven regions amplified were polymorphic, having between two and seven variable length alleles in the 11 strains of Candida albicans examined. The results of this and similar searches will facilitate epidemiological and evolutionary studies of Candida and other microorganisms.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sequence diversity at a coding-region microsatellite locus of two diploid Candida species was surveyed. Twenty-one alleles from fourteen strains of Candida albicans and three alleles from two strains of the closely related Candida dubliniensis were sequenced. Results show independent length variation in two contiguous hexanucleotide repeats, one non-contiguous hexanucleotide repeat, and two non-contiguous trinucleotide repeats within a 120 bp coding region. A neighboring, non-repetitive 120 bp region showed no variation. The information density of sequence polymorphisms in this region provides a powerful tool for genotyping microorganisms in epidemiological studies, yielding detailed resolution of closely related strains, and clearly distinguishing the two species studied here. The individual length-variable repeat regions are very short (2–8 repeats), demonstrating that even very short microsatellites can show high levels of length variability when surrounded by similarly repetitive DNA. Extensive homoplasy was discovered among the C. albicans alleles, with the majority of overall length categories consisting of alleles with more than one sequence. Our results show that microsatellite length alone should not be used to assume either sequence identity or identity by descent. Microsatellite length mutations appear to have generated the high degree of both inter- and intraspecific polymorphism seen at the ERK1 locus, and form an island of variability in an otherwise well-conserved gene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have demonstrated hypervariability of native short-motif repeats (microsatellites) in Escherichia coli. Twenty-five of the longest microsatellites in the E. coli genome were identified. These were analysed for length variability among 22 wild-type (non-mutator) isolates from the E. coli collection of reference (ECOR). Non-coding mononucleotide repeats are consistently polymorphic among these genetically diverse E. coli. Length differences in variable microsatellites allowed all E. coli strains examined to be uniquely differentiated. Phylogenetic analysis of the variable repeats shows ubiquitous homoplasy at the level of divergence represented by the sample set, suggesting that these markers are hypermutable and should prove valuable for the discrimination of closely related strains that are not otherwise genetically differentiable. Genomic analyses suggest that similar markers are also likely to be found in all other prokaryotes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 374 (1995), S. 833-834 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THIS short book is the latest in the Science Masters series, a set of brief explorations of their fields of expertise by some of today's most distinguished science writers. Richard Dawkins treats the subject of evolution in his usual limpid style. The book breaks no new ground but, as usual, it ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 359 (1992), S. 438-439 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Philosophical Transactions of the Royal Society: Biological Sciences (Series B).Editor Quentin Bone.Royal Society. 12/yr. UK £525; elsewhere £560, $1,120.Proceedings of the Royal Society: Bio-logical Sciences (Series B).Editor Bryan C. Clarke.Royal Society. 12/yr. UK £200; ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 364 (1993), S. 113-113 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THIS book is an expansion of the Reith lectures that the geneticist Steve Jones gave on British Broadcasting Corporation radio in 1991. It was with some bemuse-ment that I realized that substantial numbers of people in England still sit down and listen, for tens of minutes at a time, while somebody ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 389-390 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - The superb sets of human mitochondrial tree data collected by Cann et aLl and Vigilant et al.2 have turned out to be remarkably difficult to analyse in a way that can yield a consistent story about human origins. The possibility that the data show an African mitochondrial 'Eve' ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 363 (1993), S. 313-314 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] GOOD textbooks shape a field. They present up-to-date information in such a well-organized way that gaps in our knowledge become glaringly apparent. Alert students who read such books are driven to ask how these gaps might be filled in, and sometimes to ask even more fundamental questions about the ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 361 (1993), S. 30-30 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] I AM fond of saying that inside every fat book there is a thin one screaming to get out. This book is an exception - it is a thin book, but, defying logic, there is a fat one inside screaming to get out. Bruce Wallace provides us with a highly personal, highly selective and - dare I say it ...
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