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  • lake trout  (2)
  • Biochemistry and Biotechnology  (1)
  • Cell & Developmental Biology  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Polymorphism of the nucleolus organizer region (NOR) on the putative sex chromosomes of Arctic char (Salvelinus alpinus) is not sex related (1997)
    Springer
    Chromosome research 5 (1997), S. 221-227 
    Details
    ISSN: 1573-6849
    Schlagwort(e): Arctic char ; fluorescence in situ hybridization ; heterochromatin ; lake trout ; nucleolus organizer region ; sex chromosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Polymorphism of the nucleolus organizer region (NOR) on the putative sex chromosomes of Arctic char (Salvelinus alpinus) was examined using conventional cytogenetic and molecular techniques. Variation was observed in the number, size and position of rDNA loci on the sex pair. Fluorescence in situ hybridization (FISH) analyses showed that the sex chromosomes of Arctic char lack the repetitive DNA sequences (MboI/BglII family) that are a prominent feature of the sex chromosomes of lake trout (S. namaycush). Southern analyses of genomic DNAs using an rDNA fragment as probe revealed extensive restriction fragment length polymorphism (RFLP) variation among individuals. Despite the presence of variation in all aspects of this rDNA locus, no sex-specific differences were detected. Repetitive DNAs (multicopy rDNA as in Arctic char or tandem repetitive DNA as in lake trout) appear to play important but different roles in the evolution of the sex chromosomes in these species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018411417816
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  • 2
    Digitale Medien
    Digitale Medien
    Structure and Organization of the rDNA Intergenic Spacer in Lake Trout (Salvelinus namaycush) (2000)
    Springer
    Chromosome research 8 (2000), S. 5-16 
    Details
    ISSN: 1573-6849
    Schlagwort(e): intergenic spacer (IGS) ; lake trout ; ribosomal DNA ; salmonid ; Salvelinus namaycush
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A total-genomic cosmid library was created to isolate complete copies of the rDNA cistron of lake trout (Salvelinus namaycush) in order to study the structure and organization of the intergenic spacer (IGS) in this species. A total of 60 rDNA- positive clones (average inserts 〉 25 kb) was recovered by screening the library with a rDNA-specific probe. Positive clones were assayed for the presence of the two internal rDNA spacers (ITS-1 and ITS-2) and the entire IGS fragment was successfully amplified from 42 clones by PCR. Length of the IGS fragments ranged from 9.4 to 17.8 kb. Comparative restriction mapping of the IGS–PCR products of several clones indicated two regions of extensive length variation surrounding a central region with sequence conservation. DNA sequence analysis was used to investigate the molecular basis of the IGS length variation and focused on identifying the region responsible for this variation. Over 9 kb of DNA sequence was obtained for one clone (A1) with a total IGS length of approximately 12.4 kb. Sequence of a conserved central region contained two open reading frames and a number of short direct repeats. Length variation in the IGS was determined by RFLP to result from differences in the number of copies of repetitive DNA sequences. These included an 89-bp tandem repeat (α repeats), an 82-bp element (β repeats), a 168–177-bp element (S repeats), and a 179–201-bp element (δ repeats). Overall nucleotide composition of the IGS was biased towards A and T (%GC = 47.4). Maintenance of discrete rDNA-length variants in lake trout suggests that the rate of gene conversion is insufficient to produce homogeneous copies across the genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009214800251
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  • 3
    Digitale Medien
    Digitale Medien
    Induction of paternal genome loss by the paternal-sex-ratio chromosome and cytoplasmic incompatibility bacteria (Wolbachia): A comparative study of early embryonic events (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 408-418 
    Details
    ISSN: 1040-452X
    Schlagwort(e): Paternal genome loss ; Cytoplasmic incompatibility ; Paternal-sex-ratio chromosome ; Wolbachia ; Nasonia ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Paternal genome loss (PGL) during early embryogenesis is caused by two different genetic elements in the parasitoid wasp, Nasonia vitripennis. Paternal sex ratio (PSR) is a paternally inherited supernumerary chromosome that disrupts condensation of the paternal chromosomes by the first mitotic division of fertilized eggs. Bacteria belonging to the genus Wolbachia are present in Nasonia eggs and also disrupt paternal chromosome condensation in crosses between cytoplasmically incompatible strains. Cytoplasmic incompatibility Wolbachia are widespread in insects, whereas PSR is specific to this wasp. PGL results in production of male progeny in Nasonia due to haplodiploid sex determination. The cytological events associated with PGL induced by the PSR chromosome and by Wolbachia were compared by fluorescent light microscopy using the fluorochrome Hoescht 33258. Cytological examination of eggs fertilized with PSR-bearing sperm revealed that a dense paternal chromatin mass forms prior to the first metaphase. Quantification of chromatin by epifluorescence indicates that this mass does undergo replication along with the maternal chromatin prior to the first mitotic division but does not replicate during later mitotic cycles. Contrary to previous reports using other staining methods, the paternal chromatin mass remains condensed during interphase and persists over subsequent mitotic cycles, at least until formation of the syncytial blastoderm and cellularization, at which time it remains near the center of the egg with the yolk nuclei. Wolbachia-induced PGL shows several marked differences. Most notable is that the paternal chromatin mass is more diffuse and tends to be fragmented during the first mitotic division, with portions becoming associated with the daughter nuclei. Nuclei containing portions of the paternal chromatin mass appear to be delayed in subsequent mitotic divisions relative to nuclei free of paternal chromatin. Crosses combining incompatibility with PSR were cytologically similar to Wolbachia-induced PGL, although shearing of the paternal chromatin mass was reduced. Wolbachia may, therefore, block an earlier stage of paternal chromatin processing in the fertilized eggs than does PSR. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080400404
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  • 4
    Digitale Medien
    Digitale Medien
    Method development in pharmaceutical analysis employing capillary electrochromatography (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2073-2082 
    Details
    ISSN: 0173-0835
    Schlagwort(e): Capillary electrochromatography ; Pharmaceuticals ; Polar neutral pharmaceuticals ; Pharmaceutical analysis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Capillary electrochromatography (CEC) has been employed to explore method development for a series of structurally related polar neutral compounds of pharmaceutical relevance. Capillaries with dimensions of 75 μm ID × 25 cm length (34.5 cm total) were packed with Spherisorb ODS-1, Hypersil phenyl, and Hypersil MOS (all 3 μm particles) and were compared in the reversed-phase mode in order to determine which phase provided the best initial performance and thus serve as the phase of choice for additional method development experiments. The various separation parameters examined for their effect on efficiency, k, resolution, and linear velocity included percent and type of organic modifier, buffer concentration, voltage, and temperature. All separations were conducted with an acidic mobile phase (aqueous mobile phase component, pH 3.0). The separation efficiencies obtained were on the order of 200000-260000 plates/m, which equates to reduced plate heights of 1.22 for columns packed with Spherisorb ODS-1. Repeatable column-to-column separation performance was demonstrated.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elps.1150191206
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