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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 39 (1994), S. 452-465 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Y chromosome ; Male fertility genes ; Lampbrush loops ; Germ line ; Transposable elements ; Gypsy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract During the evolution of the Y chromosome of Drosophila hydei, retrotransposons became incorporated into the lampbrush loop pairs formed by several of the male fertility genes on this chromosome. Although insertions of retrotransposons are involved in many spontaneous mutations, they do not affect the functions of these genes. We have sequenced gypsy elements that are expressed as constituents of male fertility gene Q in the lampbrush loop pair Nooses. We find that these gypsy elements are all truncated and specifically lost those sequences that may interfere with the continuity of lampbrush loop transcription. Only defective coding regions are found within the loop. Gypsy is not transcribed in loops of many other Drosophila species harboring the family. These results suggest that any contribution of gypsy to the function of male fertility gene Q does not depend on a conserved DNA sequence.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 199 (1990), S. 251-280 
    ISSN: 1432-041X
    Schlagwort(e): Spermatogenesis ; Drosophilia ; Y chromosomal lampbrush loops ; Male sterile mutations ; Cellular differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We constructed balancer-chromosomes for the large autosomes ofDrosophila hydei and screened more than 16000 chromosomes for male sterile mutations in order to dissect spermatogenesis genetically. 365 mutants on the X chromosome and the autosomes 2, 3, and 4 were recovered and analysed cytologically in squash preparations under phase-contrast optics. The majority of the mutations allows a rather advanced differentiation of the spermatozoa. At the light-microscopical level, it is possible to classify these mutations with respect to individualization, coiling or motility of the mutant spermatozoa. In contrast, a small number of mutants exhibits conspicuous, pleiotropic phenotypes. Gonial divisions, the shaping of the spermatocyte nucleus and male meiotic divisions are controlled by X chromosomal or autosomal genes which can mutate to male sterile alleles. A number of nonallelic 3rd chromosome male sterile mutations interfere with the unfolding of the Y chromosomal lampbrush loops. Other autosomal male sterile mutations modify the morphology of these lampbrush loops. Another group of mutations inhibits the formation of the nebenkern while the development of the spermatid nucleus and the flagellum can proceed. Such male sterile mutations can decouple the development of nucleus, protein body, nebenkern, and flagellum of the spermatid. Thus, we can describe spermatogenesis inDrosophila as the coordinate execution of the individual developmental programs of the different components of the spermatozoon.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-2145
    Schlagwort(e): Tobacco ; Pollen ; Transcriptional control ; GT-1 · GT-2
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract TheNTP303 gene of tobacco is expressed only in bicellular pollen. The minimal pollen-specific promoter of the gene is located between −103 and −51 upstream of the transcriptional start site. Using gel mobility shift assays, we demonstrated that this minimal functional promoter interacts with a leaf nuclear GT-1 binding activity. This finding suggests that ubiquitous transcription factors are involved in the pollen-specific expression of the gene in vivo.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We present the analysis of genomic DNA fragments that were isolated as potential segments of the lampbrush loop pair Nooses on the short arm of the Y chromosome of Drosophila hydei. More than 300 kb of DNA were recovered in BamHI lambda and cosmid clone groups. This DNA is composed of the Y-specific ayl family of repetitive DNA sequences, and of other repetitive DNA sequences, which at least in part are also located elsewhere in the genome (Y-associated sequences). Two additional classes of DNA fragments were obtained from an EcoRI libary. One of them consists of ayl repeats without apparent interspersion, including a total of more than 300 kb of DNA. The other is composed of tandemly repeated YsI sequences, a Y-specific sequence derived from ayl. This class includes more than 400 kb of DNA, which is also not interspersed by other sequences. Our results show that only the ayl repeats interspersed by Y-associated DNA sequences can represent parts of the 260 kb transcription unit forming the lampbrush loop, whereas the ayl and YsI repeats without interspersion form separate and nontranscribed clusters of repetitive DNA.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We have used fluorescence in situ hybridization to map the positions of the different repetitive DNA sequences from the region forming the lampbrush loop pair Nooses on the Y chromosome of Drosophila hydei. This region harbours a megabase cluster of tandemly organized repeats of the Y-specific ay1 family and a megabase cluster of tandem repeats of the related Y-specific YsI family. In addition, ay1 repeats also occur in short blocks that are interspersed by other repetitive DNA sequences that we call Y-associated, since they have additional copies on other chromosomes. Using specific probes for ay1, YsI and Y-associated DNA sequences, we show that there is one large proximal cluster of YsI repeats and one, more distally located, large cluster of ay1 repeats. The Y-chromosomal copies of the Y-associated sequences are located in the most distal part of the ay1 cluster. This is consistent with the juxtaposition of ay1 and Y-associated sequences in more than 300 kb of cloned genomic DNA. Since both ay1 and Y-associated sequences have been shown to be transcribed in the Nooses, the lampbrush loop is formed in a distal region of the short arm of the Y chromosome, adjacent to the terminally located nucleolus organizer region. The clusters of homogeneous ay1 and YsI repeats are of no functional significance for the formation of the lampbrush loop.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Y chromosome ; Fertility genes Lampbrush loops ; Repetitive DNA sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The short arm of the Y chromosome of Drosophila hydei carries a single male fertility gene, gene Q, which forms the lampbrush loop pair Nooses. Conflicting observations have been reported concerning the identity of the repetitive DNA sequences that are transcribed in this loop pair. It has been claimed by other investigators that the loop transcripts contain repeats of two distinct, but related families of Y-specific repetitive DNA sequences, ayl and YsI. We reinvestigated this issue, using as probes single ayl and YsI repeats which, under stringent conditions, hybridize only to members of their own family. Under non-stringent conditions, both repeats hybridize in situ to Nooses transcripts. However, if hybridization conditions are stringent, only the ayl probe hybridizes to loop transcripts. Hybridizations to Northern blots of testis RNA confirm these results. Further, YsI repeats are not found the closely related species D. eohydei. We conclude that the YsI repeats are not relevant for the function of fertility gene Q.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Fertility genes ; Y chromosome Lampbrush loops ; Repetitive DNA sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Y chromosomal lampbrush loop-forming male fertility genes of Drosophila consist mainly of repetitive DNA sequences that do not code for proteins. We investigated whether differences in the transcription of these sequences can be detected in male-sterile alleles of male fertility gene Q, which forms the loop pair Nooses. The loop consists, for approximately two-thirds, of repeats of the Y-specific ay1 family of repetitive DNA sequences. Of the remaining one-third, at least one-half is represented by defective retrotransposons of the gypsy family. Both sequence types are interspersed throughout the loop. Using both ay1 and gypsy sequences as probes for transcript in situ hybridization, we show that, at the level of the light microscope, transcription of neither sequence is detectably affected in the loops formed by a male-sterile allele of gene Q. We conclude that the transcription of ay1 and gypsy is required, but not sufficient for the function of gene Q.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    BioEssays 18 (1996), S. 317-323 
    ISSN: 0265-9247
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The Y chromosomes of most Drosophila species are necessary for male fertility but they are not involved in sex determination. They have many puzzling properties that resemble the effects caused by B chromosomes. Classical genetic and molecular studies reveal substantial affinities between Y and B chromosomes and suggest that the Y chromosomes of Drosophila are not degenerated homologues of the X chromosomes, but rather that their Y chromosomes evolved as specialized supernumeraries similar to classical B chromosomes.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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