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  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The distributions of Penelope and Ulysses, two transposable elements that can induce hybrid dysgenesis, were studied in several species groups of Drosophila. No significant hybridization to Penelope and Ulysses probes was detected by Southern blot analyses of species outside the virilis group. In contrast, both element families have had a long residence in all species of the virilis species group, as indicated by their strong presence in the heterochromatic chromocenter. Except for D. kanekoi, D. lummei, and some strains of D. virilis, species of the group carry full-sized, and at least potentially functional, copies of both element families. Consistent with the occurrence of recent transposition, Penelope and Ulysses elements are located at different chromosomal sites in different geographical strains of the same species. A total of 79 Penelope and 47 Ulysses euchromatic insertion sites were localized to chromosomal subsections in species of the virilis group. Highly significant deviations from independence of the distributions of Penelope and Ulysses and previously established inversion breakpoints were documented, suggesting that these transposable elements may have played an important role in genomic reorganization and evolution of the virilis species group, which is especially rich in karyotypic variation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The Penelope family of transposable elements (TEs) is broadly distributed in most species of the virilis species group of Drosophila. This element plays a pivotal role in hybrid dysgenesis in Drosophila virilis, in which at least four additional TE families are also activated. Here we present evidence that the Penelope family of elements has recently invaded D. virilis. This evidence includes: (1) a patchy geographical distribution, (2) genomic locations mainly restricted to euchromatic chromosome arms in various geographical strains, and (3) a high level of nucleotide similarity among members of the family. Two samples from a Tashkent (Middle Asia) population of D. virilis provide further support for the invasion hypothesis. The 1968 Tashkent strain is free of Penelope sequences, but all individuals collected from a 1997 population carry at least five Penelope copies. Furthermore, a second TE, Ulysses, has amplified and spread in this population. These results provide evidence for the Penelope invasion of a D. virilis natural population and the mobilization of unrelated resident transposons following the invasion.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 253 (1975), S. 755-756 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The dictum that spontaneous crossing over does not occur in D. melanogaster males has been widely accepted since the early reports of Morgan9. Non-trivial frequencies are therefore indicative of unusual genetic events. We estimated the frequency of recombination in the third chromosome of Fl males ...
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 393 (1998), S. 22-23 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Large-scale genomic sequencing has revealed that a huge fraction of many eukaryotic genomes consists of transposable elements (transposons). These are mobile DNA sequences — ranging in size from several hundred to many thousands of base pairs — that can ‘jump’ from one ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 362 (1993), S. 202-202 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It is an ancient Mariner And he stoppeth one of three. QUESTIONS about the origin and evolutionary age of mobile genetic elements have been around since Barbara McClin-tock first described 'controlling elements' in maize almost half a century ago. Now, with the help of the polymerase chain reaction ...
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  • 6
    ISSN: 1432-1432
    Keywords: Key words: Phylogenetic analysis — Transposable elements — Horizontal transfer —Drosophila—Sophophora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A phylogenetic analysis of P transposable elements in the Drosophila obscura species group is described. Multiple P sequences from each of 10 species were obtained using PCR primers that flank a conserved region of exon 2 of the transposase gene. In general, the P element phylogeny is congruent with the species phylogeny, indicating that the dominant mode of transmission has been vertical, from generation to generation. One manifestation of this is the distinction of P elements from the Old World obscura and subobscura subgroups from those of the New World affinis subgroup. However, the overall distribution of elements within the obscura species group is not congruent with the phylogenetic relationships of the species themselves. There are at least four distinct subfamilies of P elements, which differ in sequence from each other by as much as 34%, and some individual species carry sequences belonging to different subfamilies. P sequences from D. bifasciata are particularly interesting. These sequences belong to two subfamilies and both are distinct from all other P elements identified in this survey. Several mechanisms are postulated to be involved in determining phylogenetic relationships among P elements in the obscura group. In addition to vertical transmission, these include retention of ancestral polymorphisms and horizontal transfer by an unknown mating-independent mechanism.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Genetica 107 (1999), S. 103-111 
    ISSN: 1573-6857
    Keywords: Drosophila ; genome evolution ; model organisms ; transposons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Model organisms have proved to be highly informative for many types of genetic studies involving ‘conventional’ genes. The results have often been successfully generalized to other closely related organisms and also, perhaps surprisingly frequently, to more distantly related organisms. Because of the wealth of previous knowledge and their availability and convenience, model organisms were often the species of choice for many of the earlier studies of transposable elements. The question arises whether the results of genetic studies of transposable elements in model organisms can be extrapolated in the same ways as those of conventional genes? A number of observations suggest that special care needs to be taken in generalizing the results from model organisms to other species. A hallmark of many transposable elements is their ability to amplify rapidly in species genomes. Rapid spread of a newly invaded element throughout a species range has also been demonstrated. The types and genomic copy numbers of transposable elements have been shown to differ greatly between some closely related species. Horizontal transfer of transposable elements appears to be more frequent than for nonmobile genes. Furthermore, the population structure of some model organisms has been subject to drastic recent changes that may have some bearing on their transposable element genomic complements. In order to initiate discussion of this question, several case studies of transposable elements in well-studied Drosophila species are presented.
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  • 8
    ISSN: 1573-6857
    Keywords: Drosophila melanogaster ; P elements ; population studies ; transposable elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The use of transposable elements (TEs) as genetic drive mechanisms was explored using Drosophila melanogaster as a model system. Alternative strategies, employing autonomous and nonautonomous P element constructs were compared for their efficiency in driving the ry+ allele into populations homozygous for a ry- allele at the genomic rosy locus. Transformed flies were introduced at 1%, 5%, and 10% starting frequencies to establish a series of populations that were monitored over the course of 40 generations, using both phenotypic and molecular assays. The transposon-borne ry+ marker allele spread rapidly in almost all populations when introduced at 5% and 10% seed frequencies, but 1% introductions frequently failed to become established. A similar initial rapid increase in frequency of the ry+ transposon occurred in several control populations lacking a source of transposase. Constructs carrying ry+ markers also increased to moderate frequencies in the absence of selection on the marker. The results of Southern and in situ hybridization studies indicated a strong inverse relationship between the degree of conservation of construct integrity and transposition frequency. These finding have relevance to possible future applications of transposons as genetic drive mechanisms.
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  • 9
    Publication Date: 2000-06-29
    Print ISSN: 0009-5915
    Electronic ISSN: 1432-0886
    Topics: Biology , Medicine
    Published by Springer
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  • 10
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