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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 96 (1988), S. 159-170 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract pSP64/65 subclones of four different families of repetitive sequences on the Y chromosome of Drosophila hydei were used for in vitro synthesis of labelled RNA. Pairs of RNA probes of opposite strand polarity were employed to analyse RNAs transcribed on, or associated with, various Y chromosomal lampbrush loops in nuclei of primary spermatocytes of D. hydei. The results of RNA filter analysis and in situ hybridization experiments can be generalized as follows: (1) Y-specific transcripts are heterogeneous in length and are synthesized on lampbrush loops. (2) Transcription of tandemly repeated sequences is usually strand specific. (3) Members of the same sequence family can be found in transcripts from different lampbrush loops. (4) Transcripts not coded by the Y chromosome are accumulated on different subregions of Y chromosomal lampbrush loops.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 96 (1988), S. 145-158 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The sequence organization of four different families of Y chromosomal repetitive DNA is characterized at three levels of spatial extension along the Y chromosome of Drosophila hydei. At the lowest level of resolution, DNA blot analysis of Y chromosomal fragments of different lengths and in situ hybridization experiments on metaphase chromosomes demonstrate the clustering of each particular sequence family within one defined region of the chromosome. At a higher level of resolution, family specific repeats can be detected within these clusters by crosshybridization within 10–20 kb long continuous stretches of cloned DNA in EMBL3 phages. At the highest level of resolution, detailed sequence analysis of representative subclones about 1 kb in length reveals a satellite-like head to tail arrangement of family specific degenerated subrepeats as the building scheme common to all four families. Our results provide the first comparative sequence analysis of three novel families of repetitive DNA on the long arm of the F chromosome of D. hydei. Additional data are presented which support the existence of two related subfamilies of repetitive DNA on the short arm of the Y chromosome.
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  • 3
    ISSN: 1617-4623
    Keywords: Y chromosomal lampbrush loops ; Drosophila hydei cell line KUN-DH-33 ; PFGE of repetitive DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The understanding of structure and function of the so-called fertility genes of Drosophila is very limited due to their unusual size — several megabases — and their location on the heterochromatic Y chromosome. Since mapping of these genes has mainly been done by classical cytogenetic analyses using a small number of cytologically visible lampbrush loops as the sole markers for particular fertility genes, the resolution of the genetic map of the Y chromosome is restricted to 3–5 Mb. Here we demonstrate that a substantially finer subdivision of the megabase-sized fertility genes in the subtelomeric regions of the Y chromosome of Drosophila hydei can be achieved by a combination of digestion with restriction enzymes having 6 by recognition sequences, and pulsed field gel electrophoresis. The physical subdivision is based upon large conserved fragments of repetitive DNA in the size range from 50 up to 1600 kb and refers to the long-range organization of several families of repetitive DNA involved in Y chromosomal transcription processes in primary spermatocytes. We conclude from our results that at least five different families of repetitive DNA specifically transcribed on the lampbrush loops nooses and threads are organized as extended clusters of several hundred kb, essentially free of interspersed non-repetitive sequences.
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  • 4
    ISSN: 1573-5028
    Keywords: polypeptide genes ; photosystem I ; thylakoid membrane ; plastid DNA ; transcripts ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A photosystem I reaction center complex has been purified to homogeneity by a procedure involving partial solubilization of spinach thylakoid membranes, ion exchange chromatography and centrifugation in sucrose gradients. The complex contains 7 polypeptides: the P700 chlorophylla apoprotein with an apparent molecular weight of 67 kd, which at high resolution splits into two bands, and smaller polypeptides of 22 (subunit 2), 18.5, 18, 16, 12 and 10 kd. Stable transcripts for the P700 chlorophylla apojprotein and subunit 2 were found in plastid and cytosolic RNA, respectively. The apoprotein product obtained by translation in a mRNA-dependent cell-free rabbit reticulocyte lysate and also by DNA-programmed transcription-translation of cloned plastid DNA fragments inE. coli lysates was indistinguishable immunologically and electrophoretically from the authentic protein. However, the product immunologically related to subunit 2 was 4 kd larger than the mature compound indicating that this protein is encoded in the nucleus and synthesized as a precursor. The gene for the P700 chlorophylla apoprotein has been physically mapped on the spinach plastid chromosome by hybrid selection mapping and DNA-programmed cell-free transcription-translation using cloned restriction fragments of plastid DNA. There is one gene copy per chromosome and it is located centrally in the large single-copy region of the circular DNA molecule. This gene is uninterrupted and is transcribed in the same direction as that of the large subunit of ribulose bisphosphate carboxylase/oxygenase. Its transcript is approximately 4 kb longer than the 2 kbp structural gene.
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  • 5
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-6849
    Keywords: coaxial transcript shells ; Drosophila hydei cell line KUN-DH-33 ; pulsed-field gel electrophoresis of repetitive DNA ; two-colour transcript fluorescencein situ hybridization ; Y chromosomal lampbrush loopsThreads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The results of pulsed-field gel electrophoresis (PFGE) analysis and two-colour transcript fluorescencein situ hybridization (FISH) for the threeThreads-specific DNA satellitesYLII, YLI andrally are in support of long-range clustering of these sequence families within the subterminal region on the long arm of the Y chromosome ofDrosophila hydei. On the basis of the linear arrangement of at least four extended clusters of satellite-specific sequences, the loop morphology of wild-type and several mutantThreads can be explained by assumption of a singleThreads-specific transcription unit comprising about 5.1 Mb of repetitive DNA located between thePseudonucleolus and theNucleolus organizer. Transcription is unidirectional from thePseudonucleolus towards the terminally locatedNucleolus organizer. Transcripts most likelly start in front of or within the 3.2 Mb region ofYLII-related sequences, pass through subsequent blocks of 1.2 and 0.3 Mb ofYLI- andrally-related sequences, respectively, and cease within the region of a smaller block ofYLI-related repeats. The megabase-sized transcripts remain physically linked to the DNA axis and their extended satellite-specific regions from coaxial clouds or shells around the central DNA axis. In this way each cluster of earlier-transcribed sequences generates a cloud or shell on top of the later-transcribed ones. According to this model of ‘satellite-specific coaxial shells’ the tube-like morphology and other peculiarities of the Y chromosomal lampbrush loopsThreads can be explained as a result of satellitespecific RNA superstructures and/or formation of extended ribonucleoprotein (RNP) complexes between clusters of satellite-specific transcripts and specific proteins. On the basis of this model the specific morphology of severalThreads mutants can be interpreted as the result of large interstitial or terminal deletions that alter the total length of theThreads-specific transcription unit without exerting other major effects on principal features of the transcription process along theThreads.
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  • 7
    ISSN: 1573-6857
    Keywords: Y chromosome ; fertility gene ; lampbrush loop ; satellites ; transposable elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fertility genes on the heterochromatic Y chromosome of various Drosophilaspecies are unique for several reasons. Most of them are megabase-sized. Their expression is restricted to premeiotic spermatocytes and often associated with unfolding of huge species-specific lampbrush loops. Molecular analysis of the orthologous dynein genes Dhc-Yh3, DhDhc7(Y)and DeDhc7(Y)on the Y chromosome of the three species D. melanogaster, D. hydeiand D. eohydei, respectively, revealed that the megabase gene size as well as the species-specific morphology of the corresponding lampbrush loops kl-5, Threadsand diffuse loopsresult from huge introns and their specific sequence composition, whereas the majority of all 20 introns in each of the three genes is in a size of 45–72 bp. The loop-specifying introns are extreme exceptions due to extended assemblies of degenerated transposable elements and/or large clusters of satellite DNAs. Here we use sequence information from the complete intron sets of three orthologous Y chromosomal dynein genes to deduce a scenario for an evolutionary pathway leading to the megabase-sized genes on the heterochromatic Y chromosome of Drosophila. The obvious bias between very small and species-specific mega introns is explained as the result of an autocatalytic mode of intron growth. An initial coincidental hit by a single transposable element extends the size of a 50 bp intron for about two orders of magnitude and determines it for preferential extension by similar insertion events. This phase of continuous moderate growth is followed by rapid size enlargements by repeating amplifications generating extended clusters of satellite DNA. Size control by recombination, on the other hand, is suppressed in Drosophilamales by achiasmatic meiosis.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 1847-1853 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Acrylamide (1) and p-nitrophenyl acrylate (2) can be copolymerized in any relative molar proportion by using azoisobutyronitrile as initiator and dimethylsulphoxide as solvent. Under different reaction conditions the degree of polymerization was found between 200 and 500. At the early stage of polymerization 2 is more frequently incorporated in the copolymers than 1. The copolymers are highly soluble in dimethylsulphoxide and react very easily with aliphatic or aromatic primary amines. Treatment of a copolymer with dry ammonia gas yields the corresponding polyacrylamide within a few minutes.
    Notes: Acrylamid (1) und p-Nitrophenylacrylat (2) lassen sich mit Azoisobuttersäuredinitril in Dimethylsulfoxid in jedem molaren Verhältnis polymerisieren. Je nach Reaktionsbedingungen entstehen Copolymere, deren mittlerer Polymerisationsgrad zwischen 200 und 500 liegt. Dabei wird 2 zu Beginn der Polymerisation etwas bevorzugt eingebaut. Die Copolymeren sind in Dimethylsulfoxid sehr gut löslich und zeichnen sich durch ihre hervorragende Reaktivität gegenüber primären aliphatischen und aromatischen Aminen aus. So werden sie durch Behandlung mit trockenem Ammoniak in wenigen Minuten glatt in die entsprechenden Polyacrylamide überführt.
    Additional Material: 1 Ill.
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