oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
5S rDNA characterization in twelve Sciaenidae fish species (Teleostei, Perciformes): depicting gene diversity and molecular markers
Alves-Costa, Fernanda A.;Martins, Cesar;Matos, Fernanda Del Campos de;Foresti, Fausto;Oliveira, Claudio;Wasko, Adriane P.;
Genetics and Molecular Biology , 2008, DOI: 10.1590/S1415-47572008000200025
Abstract: in order to extend the genetic data on the sciaenidae fish family, the present study had the purpose to characterize pcr-generated 5s rdna repeats of twelve species of this group through page (polyacrylamide gel electrophoresis) analysis. the results showed the occurrence of at least two different 5s rdna size classes in all the species. moreover, 5s rdna repeats of one of the studied species - isopisthus parvipinnis - were cloned and subjected to nucleotide sequencing and southern blot membrane hybridization analyses, which permitted to confirm the existence of two major 5s rdna classes. phylogenetic analysis based on the nucleotide sequences of different 5s rdna repeats of i. parvipinnis lead to their separation into two major clusters. these results may reflect the high dynamism that rules the evolution rate of 5s rdna repeats. the obtained data suggest that 5s rdna can be useful in genetic analyses to identify species-specific markers and determine relationships among species of the sciaenidae group.
Chromosomal location of 18S and 5S rDNA sites in Triportheus fish species (Characiformes, Characidae)
Diniz, Débora;Laudicina, Alejandro;Bertollo, Luiz Antonio Carlos;
Genetics and Molecular Biology , 2009, DOI: 10.1590/S1415-47572009005000017
Abstract: the location of 18s and 5s rdna sites was determined in eight species and populations of the fish genus triportheus by using fluorescent in situ hybridization (fish). the males and females of all species had 2n = 52 chromosomes and a zz/zw sex chromosome system. a single 18s rdna site that was roughly equivalent to an ag-nor was detected on the short arms of a submetacentric pair in nearly all species, and up to two additional sites were also observed in some species. in addition, another 18s rdna cluster was identified in a distal region on the long arms of the w chromosome; this finding corroborated previous evidence that this cluster would be a shared feature amongst triportheus species. in t. angulatus, a heterozygotic paracentric inversion involving the short arms of one homolog of a metacentric pair was associated with nors. the 5s rdna sites were located on the short arms of a single submetacentric chromosomal pair, close to the centromeres, except in t. auritus, which had up to ten 5s rdna sites. the 18s and 5s rdna sites were co-localized and adjacent on the short arms of a chromosomal pair in two populations of t. nematurus. although all triportheus species have a similar karyotypic macrostructure, the results of this work show that in some species ribosomal genes may serve as species-specific markers when used in conjunction with other putatively synapomorphic features.
Physical mapping of the 18S and 5S ribosomal genes in nine Characidae species (Teleostei, Characiformes)
Peres, Wellington Adriano Moreira;Bertollo, Luiz Antonio Carlos;Moreira Filho, Orlando;
Genetics and Molecular Biology , 2008, DOI: 10.1590/S1415-47572008000200009
Abstract: characidae is one of the largest fish families of the neotropical region, and presenting a pronounced morphological variability, certainly does not constitute a monophyletic group. the cytogenetical data also show a large chromosomal variation and can provide important information for a better understanding of the relationships between the species of this group. 18s and 5s rdna probes were used in the present study for the chromosomal mapping in different characidae species from the s?o francisco river (astyanax lacustris, astyanax scabripinnis, hasemania nana, piabina argentea, orthospinus franciscensis, serrapinnus heterodon, serrapinnus piaba and myleus micans) and alto paraná (astyanax altiparanae) basins. species with a single pair of chromosomes bearing the nucleolar organizing regions (nors) were identified, as well as species with multiple nors, up to a maximum of seven 18s rdna sites. the number of 5s rdna site was also not constant, varying from two to eight. the mapping of the ribosomal genes was useful for the characterization and differentiation of the analyzed species.
Cytogenetic comparison between two allopatric populations of Astyanax altiparanae Garutti & Britski, 2000 (Teleostei, Characidae), with emphasis on the localization of 18S and 5S rDNA  [cached]
R. B. Pacheco,Renata Rosa,L. Giuliano-Caetano,H. F. Júlio Jr.
Comparative Cytogenetics , 2011, DOI: 10.3897/compcytogen.v5i3.1235
Abstract: Two populations of Astyanax altiparanae (Garutti et Britski, 2000) of the água dos Patos stream/SP and lake Igapó/PR were analyzed. All individuals showed 2n = 50, however, different karyotypic formulae were observed. The population of the água dos Patos stream showed 8m +24sm+6st+12a (NF=88) and the population of lake Igapó, 8m+28sm+4st+10a (NF=90). Nucleolus organizing regions (AgNORs) were observed in the terminal position on the short and long arm of different chromosomes of both populations, showing a variation from 3 to 4 chromosomes. Fluorescent in situ hybridization (FISH) using 18S rDNA probes revealed only one pair of chromosomes with fluorescent signals in the terminal site on the short arm in the Igapó lake population, while the population of água dos Patos stream showed 4 fluorescence terminal signals, characterizing a system of simple and multiple NORs, respectively. 5S rDNA fluorescent signals were detected in the interstitial position of a pair of chromosomes in the two studied populations. Some AgNOR sites revealed to be GC-rich when stained with Chromomycin A3 (CMA3), however, AT positive regions were not observed. The data obtained show that, despite the conservation of the diploid number and location of 5S DNAr, differences in both the distribution of 18S rDNA and karyotypic formula among the populations were found, thus corroborating the existing data on chromosome variability in Astyanax altiparanae that can be significant for cytotaxonomy in this group.
Location of 45S and 5S rDNA on Barley Chromosomes and FISH Analysis for 5S rDNA on Extended DNA Fibers
大麦45S和5S rDNA定位及5S rDNA伸展纤维的FISH分析

赵丽娟,李立家,覃瑞,熊怀阳,宋运淳
植物科学学报 , 2005,
Abstract: With the help of fluorescene in situ hybridization(FISH),we have located and analyzed the sites of the 45S and 5S rDNA on the mitotic metaphase chromosomes of barley (Hordeum vulgare L.).The results indicated that there were two pairs of signs detected for 45S rDNA,each at 1S and 2L.The signal of 5S rDNA was relatively weak,and it was located on 3L.The copy number of 5S rDNA was determined by extended DNA fiber based on DNA fiber fluorescence in situ hybridization(Fiber-FISH) in barley genome.It could be estimated that the copy number was about 408-416 for 5S rDNA.In this study,the variability of number of rDNA in genome among different barley species was discussed.
Spermiogenesis and spermatozoa ultrastructure in five species of the Curimatidae with some considerations on spermatozoal ultrastructure in the Characiformes
Quagio-Grassiotto, Irani;Gameiro, Maria Carolina;Schneider, Tatiana;Malabarba, Luiz Roberto;Oliveira, Claudio;
Neotropical Ichthyology , 2003, DOI: 10.1590/S1679-62252003000100004
Abstract: spermiogenesis in the curimatid species, steindachnerina insculpta, cyphocharax gillii, c. modestus, c. spilotus, and potamorhina altamazonica, is characterized by lateral development of the flagellum, nuclear rotation, eccentric nuclear fossa formation, and chromatin compacted into thick fibers. these spermatozoa exhibit a spherical head containing a nucleus with the chromatin highly condensed into thick fibers with small electron-lucent areas, and no acrosome. the nuclear fossa is of the moderate type and eccentric and penetrated by the centriolar complex. the midpiece is small, has many elongate vesicles, and a short cytoplasmic channel. mitochondria may be elongate, branched or c-shaped, and are separated from the initial segment of the axoneme by the cytoplasmic channel. the flagellum contains the classical axoneme structure (9+2) and has a membranous compartment in the initial region; it does not have lateral fins. only small differences were observed among the analyzed species and genera of the curimatidae. spermiogenesis and spermatozoa in the curimatidae have many of the characteristics found in almost all other characiform species. on the other hand, the presence of a membranous compartment in the initial region of curimatid flagella, a structure common in many cypriniformes spermatozoa, is unknown in other characiforms. spermiogenesis and the spermatozoa of the characiformes are discussed.
Identification and description of distinct B chromosomes in Cyphocharax modestus (Characiformes, Curimatidae)
Santos, Lessandra Viviane De Rosa;Foresti, Fausto;Martins, Cesar;Oliveira, Claudio;Wasko, Adriane Pinto;
Genetics and Molecular Biology , 2008, DOI: 10.1590/S1415-47572008000200019
Abstract: cytogenetic analyses were performed in cyphocharax modestus, collected at paranapanema river and tietê river (s?o paulo state, brazil). a karyotype with 2n = 54 chromosomes was observed in the animals from both brazilian freshwater river systems. one to four b chromosomes were also detected in individuals from the paranapanema river, which represents the probable first report of more than a single supernumerary element in a species of the curimatidae group. c-banding revealed centromeric and telomeric heterochromatin blocks in several chromosomes of the normal karyotype complement of c. modestus. moreover, while some b chromosomes were characterized by the complete absence of c-bands, others were totally heterochromatic. although there was a prevalence of b chromosomes in males of c. modestus, at least one supernumerary element was found in males and/or females of several other populations of the species, which suggests that the presence of these chromosomes seems to represent a general trait of c. modestus. a possible origin of the described b chromosomes may be related to the occurrence of a chromosome non-disjunction followed by the loss of euchromatic segments, an event that should have occurred in chromosomes that present conspicuous centromeric heterochromatic blocks and even in chromosomes that lack c-bands in this region, resulting in small supernumerary elements.
Nucleolar Association and Transcriptional Inhibition through 5S rDNA in Mammals  [PDF]
Andrew M. Fedoriw,Joshua Starmer,Della Yee,Terry Magnuson
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002468
Abstract: Changes in the spatial positioning of genes within the mammalian nucleus have been associated with transcriptional differences and thus have been hypothesized as a mode of regulation. In particular, the localization of genes to the nuclear and nucleolar peripheries is associated with transcriptional repression. However, the mechanistic basis, including the pertinent cis- elements, for such associations remains largely unknown. Here, we provide evidence that demonstrates a 119 bp 5S rDNA can influence nucleolar association in mammals. We found that integration of transgenes with 5S rDNA significantly increases the association of the host region with the nucleolus, and their degree of association correlates strongly with repression of a linked reporter gene. We further show that this mechanism may be functional in endogenous contexts: pseudogenes derived from 5S rDNA show biased conservation of their internal transcription factor binding sites and, in some cases, are frequently associated with the nucleolus. These results demonstrate that 5S rDNA sequence can significantly contribute to the positioning of a locus and suggest a novel, endogenous mechanism for nuclear organization in mammals.
Cytogenetic analyses of two Curimatidae species (Pisces; Characiformes) from the Paranapanema and Tietê Rivers
De Rosa, LVS;Foresti, F.;Martins, C.;Oliveira, C.;Sobrinho, PE.;Wasko, AP.;
Brazilian Journal of Biology , 2007, DOI: 10.1590/S1519-69842007000200020
Abstract: cytogenetic analyses were performed in two curimatidae species (steindachnerina insculpta and cyphocharax modesta) from the paranapanema and tietê rivers (s?o paulo state, brazil), showing a karyotype composed of 54 meta-submetacentric chromosomes in both species. silver- and chromomycyn-staining and fluorescent in situ hybridization (fish) using a 18s rdna probe indicated that the nucleolar organizer regions (nors) of both species are localized in the terminal region of the long arm of two metacentric chromosomes. although a single nor system was evidenced in both analyzed species, s. insculpta and c. modesta presented the nucleolar organizer regions in distinct chromosome pairs, indicating that these cistrons can be considered cytogenetic markers. variation on the amount and distribution of the constitutive heterochromatin (c-bands) could also be detected between the two species - while s. insculpta presented few heterochromatic blocks, intensely stained c-bands were evidenced in c. modesta specially in the terminal region of the long arm of the nor-bearing chromosomes. although most curimatidae species have been characterized by homogeneous karyotypes, isolated populations could be established under different environmental conditions leading to karyotype micro-structure variations specially related to the nors localization and c-banding distribution. the obtained data were useful for the cytogenetic characterization and differentiation of s. insculpta and c. modesta and could be used in evolutionary inferences in the curimatidae group.
Expression of 5S rDNA in the oocytes of water frogs
El?bieta Czarniewska, Robert Plewa
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-10
Abstract: 5S rDNA relative expression of the Rana ridibunda oocytes is approximately six times higher in comparison to the Rana lessonae oocytes. The oocytes of the investigated Rana esculenta frogs, in respect of 5S rDNA relative expression ratio, were very similar to the Rana ridibunda oocytes.We suggest the possibility of using 5S rDNA as the internal control gene, in the studies of relative mRNA quantitative assays in water frog oocytes, because of its characteristic specific expression pattern in the Rana lessonae, Rana ridibunda and Rana esculenta oocytes.An amphibian egg contains all the information required for its early post-fertilisation proliferation and differentiation. During the initial stages of development, all translated mRNAs, as well as ribosomes – the cellular organelles responsible for protein biosynthesis – originate from the mother. They play a crucial role in the success of early embryonic development, allowing the first cleavages to occur, before the activation of embryonic genome after the midblastula transition (MBT) [1,2].The eucaryotic ribosome is a macromolecular structure composed of a large (60S) and a small (40S) subunits. Biochemically, it is composed of four ribosomal RNA molecules (rRNAs) and over 70 ribosomal proteins [3]. In eukaryotes, two distinct classes of ribosomal DNA (rDNA) genes can be distinguished. Each is composed of tandemly repeated units of hundreds to thousands of copies. The transcripts of the minor class (5S rRNA) are made from one region of the genome, the transcripts of 28S, 18S and 5.8S rRNAs (the major class; 45S rDNA) from another. The 5S rDNA array consists of multiple copies of a highly conserved 120 bp coding sequence, which are separated by the variable nontranscribed spacers (NTS) [4]. The Xenopus genome contains two sets of 5S rDNA: the oocyte-type, active only in oocytes (20,000 tandemly-repeated copies per haploid genome), and the somatic-type, active in every cell (400 copies per haploid genome). The synthes
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.