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  • 1
    Electronic Resource
    Electronic Resource
    Junctions between repetitive DNAs on the PSR chromosome of Nasonia vitripennis: Association of palindromes with recombination (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 352-362 
    Details
    ISSN: 1432-1432
    Keywords: Paternal-Sex-Ratio ; Nasonia ; Repetitive DNA ; Junctions ; Recombination ; Palindromes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Paternal-Sex-Ratio (PSR) chromosome of Nasonia vitripennis contains several families of repetitive DNAs that show significant sequence divergence but share two palindromic regions. This study reports on the analysis of junctions between two of these repetitive DNA families (psr2 and psr18). Three lambda clones that hybridized to both repeat families were isolated from PSR-genomic DNA libraries through multiple screenings and analyzed by Southern blots. Analysis of clones showed a region in which the two repeat types are interspersed, flanked by uniform blocks of each repeat type. PCR amplification of genomic DNA confirmed the contiguous arrangement of psr2 and psr18 on PSR and identified an additional junction region between these repeats that was not present in the lambda inserts. We isolated and sequenced 41 clones from the lambda inserts and genomic PCR products containing junction sequences. Sequence analysis showed that all transitions between psr2 and psr18 repeats occurred near one of the two palindromes. Based on the inheritance pattern of PSR, recombination between repeats on this chromosome must be mitotic (rather than meiotic) in origin. The occurrence of exchanges near the palindromes suggests that these sequences enhance recombination between repeat units. Rapid amplification of repetitive DNA may have been an important factor in the evolution of the PSR chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163152
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular characterization of repetitive DNA sequences from a B chromosome (1992)
    Springer
    Chromosoma 101 (1992), S. 575-583 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In the parasitic waspNasonia vitripennis, certain males carry a B chromosome, called PSR (paternal sex ratio), which causes the compaction and subsequent loss of the paternal chromosomes in fertilized eggs. BecauseNasonia are haplo-diploid, this leads to the production of all-male broods. Three families (PSR2, PSR18, PSR22) of related, tandemly repetitive DNAs were shown to be present solely on the PSR chromosome. These three families shared two conserved, palindromic ANA sequences, which may play a role in either PSR function or amplification of the tandem arrays. The tandem repeat family NV79 was determined to be present on the PSR chromosome as well as on at least one of the A chromosomes. This shared repeat as well as two repeat families (NV85, NV126) that were localized on the A chromosomes were detected in two sibling species ofN. vitripennis. NV79 and NV126 were also found in the more distantly related species,Trichomalopsis dubius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00660317
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of R1 and R2 in the rDNA units of the genus Drosophila (1997)
    Springer
    Genetica 100 (1997), S. 49-61 
    Details
    ISSN: 1573-6857
    Keywords: retrotransposable elements ; reverse transcriptase ; ribosomal RNA genes ; vertical transfer ; rate of evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract R1 and R2 are non-long terminal repeat (non-LTR) retrotransposable elements that specifically insert in the 28S ribosomal RNA (rRNA) genes of insects. Using the Drosophila genus, which includes some of the best characterized insect taxa, we have conducted a number of studies on the evolution of these elements. We find that R1 and R2 are subject to the same recombinational forces that give rise to the concerted evolution of the rDNA units. The turnover of R1 and R2 elements can be readily documented in different strains of D. melanogaster using 5′ truncated elements as restriction-length polymorphisms. This turnover leads to uniform populations of elements with nucleotide sequence divergence of different copies averaging only 0.23% for the R2 and 0.47% for the R1 elements. Molecular phylogenetic analysis of elements from 16 different species of Drosophila suggests that these elements have been stable components of the rDNA locus for the 50–70 million year history of the Drosophila genus. Using changes at synonymous positions within the protein-encoding regions as estimates of the baseline substitution rate, it could be shown that R1 and R2 are evolving at rates similar to that of typical protein encoding genes provided corrections are made for the low codon bias of the elements. R1 and R2 are clearly well-adapted for their existence in the rDNA units of their host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018396505115
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    Paper (German National Licenses)
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  • 4
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    Single-frame multiparameter platforms for seafloor geophysical and environmental observations: projects and missons from GEOSTAR to ORION (2002)
    Elsevier
    In:  In: Science Technology Synergy for Research in the Marine Environment: Challenges for the XXI Century. , ed. by Beranzoli, L., Favali, P. and Smirglio, G. Developments in marine technology, 12 . Elsevier, Amsterdam, Netherlands, p. 2000. ISBN 0-7803-8669-8
    Details
    Publication Date: 2020-05-27
    Description: The paper presents an overview of recent seafloor long-term single-frame multiparameter platform developed in the framework of the European Commission and Italian projects starting from the GEOSTAR prototype. The main features of the different systems are described as well as the sea missions that led to their validation. The ORION seafloor observatory network recently developed, based on the GEOSTAR-type platforms and engaged in a deep-sea mission at 3300 m w.d. in the Mediterranean Sea, is also described
    Type: Book chapter , NonPeerReviewed
    Format: text
    DOI: 10.1109/OCEANS.2004.1406450
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    OceanRep: Book chapter
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