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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Genetic diversity was analysed in brown trout Salmo trutta populations living in an area of central Italy using RFLP analysis of two mtDNA segments and of the nuclear locus LDH-C1*. The data indicated a genetic structure profoundly altered by repeated stockings with allochthonous material of Atlantic origin. In fact, four and 11 of the haplotypes detected were, respectively, identical or genetically very close to haplotypes found in Danish populations, the putative source of stocked brown trout. Furthermore, the LDH-C1*90 allele, typical of north-western Europe, was widespread among the samples studied. Nonetheless, four populations are characterized by a high frequency of both putative autochthonous haplotypes and the LDH-C1*100 allele, common in the Mediterranean basin. These populations, sampled in areas where S. trutta is documented historically, might represent a remnant of the species’ indigenous biodiversity, showing the scope for improving the management of brown trout in central Italy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The diploid complement of the paedomorphic goby Aphia minuta ranged from 44 to 41 due to Robertsonian fusions (fundamental number=44). Data on spermatogenesis suggest that structural heterozygotes are fertile and that these chromosomal changes are not involved in a speciation process.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A histological analysis of the gonad of the pelagic crystal goby Crystallogobius linearis, from the coastal central area of the Adriatic Sea, showed it to be a truly semelparous species; after the first spawning the mature gonads of both males and females appeared to have lost the capability for further spawning. Mature females had very low fecundity (200–700 mature oocytes) and small egg size (0·2–0·55 mm) similarly to other progenetic species. This reproductive strategy is compared with that of Aphia minuta, and a possible cause for the post-reproductive mortality of the two gobies is suggested and discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Evidence is presented that apoptosis of intestinal enterocytes is implicated in adult mortality immediately after the breeding season in Aphia minuta, a paedomorphic goby that spends its whole life cycle of 〈1 year in the water column as a pelagic and planktophagous fish. This could be the first documented case in which apoptosis triggers a population dynamic process such as natural mortality in a vertebrate.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: At variance with previous reports, the paedomorphic goby Aphia minuta does not show semelparity, but abbreviate iteroparity like other small Mediterranean gobiid species. In spring, the mature ovary contains several batches of eggs at different stages of vitellogenesis. This indicates that the breeding season of A. minuta is quite long and that spawning takes place at least twice during its short lifespan, involving in each ovulatory wave different batches of oocytes which undergo vitellogenesis at different times. These observations agree with the testicular cycle data. In males, which in spring exhibit active spermiation coinciding with deposition of the first batch of oocytes, spermatogonial mitosis also resumes, eventually resulting in the production of new sperm in summer.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-6857
    Keywords: goby ; rDNA genes ; repetitive DNA ; transposable elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A molecular cytogenetic study of Gobius niger has been conducted by treating its mitotic chromosomes with silver-, CMA3- and DAPI-staining and fluorescent in situ hybridization using four multicopy or repetitive DNAs (the 28S and 5S rDNAs, the TTAGGG telomeric repeat and the mariner-like elements) as probes. In particular, the study proved the presence of NOR heteromorphism and suggested the possible role of the transposable element mariner in its genesis. In situ hybridization with the 5S rDNA probe proved the presence of just one 5S-bringing chromosome pair, whereas hybridization with the telomeric repeat revealed small bright hybridization spots, uniform in size and intensity, on each telomere of all chromosomes but no interstitial signals were noticed.
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  • 7
    ISSN: 1573-6849
    Keywords: Acanthopetalum sicanum ; chromosome banding ; Diplopoda ; Enologus oxypygum ; heterochromatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For the first time, a conventional analysis of C-banded karyotypes was carried out in two distantly related diplopod species; this revealed an impressive percentage of heterochromatin in both genomes. In Acanthopetalum sicanum (Order Callipodida) (2n = 12), heterochromatin constitutes about 60% of the total DNA in females and 56% in males, whereas in Enologus oxypygum (Order Julida) (2n = 22) it is about 67% in both sexes. Heterochromatin of the two species was found to be similar in base composition (AT rich) and heterochromatin distribution, indicating that it has accumulated in a species-specific manner. Sex-determining mechanisms of the XY type were detected in both A. sicanum and E. oxypygum. In A. sicanum, the Y presented the lowest heterochromatic content of all chromosomes in the karyotype, whereas the X presented the highest.
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  • 8
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data on the electrophoretic patterns of 20 enzyme loci were used to investigate relationships among seven Mediterranean goby species. The study evidenced different levels of genetic variability among the species. On the whole, the degrees of genetic differentiation were consistent with the current taxonomic recognition of species and genera. Phenetic and phylogenetic analyses agreed in clustering the samples in three groups, i.e. the Gobius (including Zosterisessor ophiocephalus), the Lesueurigobius species and Pomatoschiarua minutus. The taxa analysed probably evolved following the complex geological and climatic events that have been affecting the Mediterranean basin ever since the Miocene.
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  • 9
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A karyological study ofTrachurus trachurus andT. mediterraneus (Perciformes: Carangidae) was conducted by standard, fluorochrome staining (CMA3, mithramycin, quinacrine mustard, DAPI), C-, Ag-NOR, and Alu-I banding methods. The karyotypes of both species consisted of 2n = 48 chromosomes, but of different FN:T. trachurus possessed a chromosome complement of 2 metacentric and 46 acrocentric elements, fundamental number (FN) = 50 andT. mediterraneus, a chromosome complement of 4 metacentric, 4 submetacentric, 14 subtelocentric and 26 acrocentric chromosomes, FN = 70. In neither of the two taxa investigated were heteromorphic sex chromosomes observed. The nucleolar organizer region was interstitially located on the long arm of the Ist pair of chromosomes in both species, intermediate inT. mediterraneus and subterminal inT. trachurus. Constitutive heterochromatin was found in nearly all centromeric and telomeric regions inT. trachurus; inT. mediterraneus it formed less intense telomeric and centromeric bands and thin interstitial bands on eight chromosome pairs. In addition, the C-positive material reacted differently to the digestion with endonuclease Alu-l in the two species. The results are discussed and compared with karyological data known for other species of Carangidae.
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  • 10
    Publication Date: 2013-07-26
    Description: How the transcription repressing complex Polycomb interacts with transcriptional regulators at housekeeping genes in somatic cells is not well understood. By exploiting a CpG island (CGI) point mutation causing a Mendelian disease, we show that DNA binding of activating transcription factor (TF) determines histone acetylation and nucleosomal depletion commensurate with Polycomb exclusion from the target promoter. Lack of TF binding leads to reversible transcriptional repression imposed by nucleosomal compaction and consolidated by Polycomb recruitment and establishment of bivalent chromatin status. Thus, within a functional hierarchy of transcriptional regulators, TF binding is the main determinant of Polycomb recruitment to the CGI of a housekeeping gene in somatic cells.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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