Search results for "Nucleolus Organizer Region"
showing 10 items of 20 documents
Karyotype analysis, nucleolar organizer regions(NORs), and C-banding pattern of Dicentrarchus iabrax(L.) and Dicentrarchus punctatus(Block, 1792)(Pis…
1990
Chromosomes of Dicentrarchus labrax and Dicentrarchus punctatus collected from the Gulf of Palermo are examined from kidney cells. The diploid chromosome number in both species is 2n=48. Ag-NOR and C-banding analyses revealed the presence of structural chromosomal polymorphism involving pair 1.A comparative analysis among the Giemsa, NOR- and C-banded karyotypes suggests that a close phylogenetic relationship between D. labrax and D. punctatus occurs. There are evidences for a conservative evolutionary trend in this genus.
Spermatocyte chromosome banding studies inBuccinulum corneum (Prosobranchia: Neogastropoda): Variation in silver-NOR banding pattern
1990
Diploid number (2n=72), and haploid number (n=36) forBuccinulum corneum (L. 1758) collected from the Gulf of Palermo in December 1987 were determined. A simple method to obtain nucleolar organizer regions (NOR), and constitutive heterochromatin regions (C-bands) of chromosomes ofB. corneum is described. Analyses of silver-stained chromosome preparations ofB. corneum suggest that a within-individual variability in NOR-banding pattern is present in each of the five specimens analysed.
Incomplete sequence homogenization in 45S rDNA multigene families: intermixed IGS heterogeneity within the single NOR locus of the polyploid species …
2014
† Background and Aims Ribosomal sequences have become the classical example of the genomic homogenization of nuclear multigene families. Despite theoretical advantages and modelling predictions that support concerted evolution of the 45S rDNA, several reports have found intragenomic polymorphisms. However, the origins and causes of these rDNA polymorphisms are difficult to assess because seed plants show a wide range of 45S rDNA loci number variation, especially in polyploids. Medicago arborea is a tetraploid species that has a single 45S rDNA locus. This feature makes this species a suitable case study to assess the fate of ribosomal IGS homogenization in polyploid species showing nucleolu…
Chromosome Analysis and rDNA FISH in The Stag Beetle Dorcus Parallelipipedus L. (Coleoptera: Scarabaeoidea: Lucanidae)
2001
In the present work the chromosome complement (2n = 18; 8AA + XY) of the stag beetle Dorcus parallelipipedus L. (Scarabaeoidea: Lucanidae) is analyzed using conventional Giemsa staining, banding techniques and ribosomal fluorescent in situ hybridization (rDNA FISH). rDNA FISH remains the unique tool for providing a clear-cut identification of Nucleolar Organizer Regions (NORs) when conventional banding methods such as silver- and CMA3-staining proved to be inadequate. The dull, homogeneous CMA3 fluorescence of all chromosomes indicates the absence of markedly GC rich compartmentalized regions in D. parallelipipedus genome. Silver impregnation inadequacy in detecting NOR regions is to be sou…
Repetitive DNAs in the slug Milax nigricans: association of ribosomal (18S–28S and 5S rDNA) and (TTAGGG)n telomeric sequences) in the slug M. nigrica…
2003
Spermatocyte chromosomes of the slug Milax nigricans (Mollusca: Gastropoda: Pulmonata) were studied using silver staining (Ag-NOR) and fluorescent in situ hybridization (FISH) with four repetitive DNA probes [18S rDNA, 5S rDNA, (TTAGGG)n and (GATA)n]. Silver impregnation was inadequate to localize the chromosome sites of nucleolus organizer regions (NORs) since no silver dots occurred on the chromosomes at spermatogonial metaphase and a diffuse silver stainability could be observed on the bivalents at metaphase-I. Unlike silver staining, single-colour rDNA FISH consistently mapped major ribosomal sites (18S-28S rDNA) on two small-sized chromosomes in spermatogonial cells and on the correspo…
Spermatocyte chromosome analysis of Helicella virgata (Pulmonata: Helicidae): silver-stained and C-banded chromosomes.
1991
Chromosome numbers of the snail Helicella virgata from the fields of Castellammare del Golfo (Sicily) are n = 26 and 2n = 52. Silver-staining analyses of testicular cells suggest that both mitotic and meiotic chromosomes are involved in nucleolus organization. A within-individual variability in NOR-banding pattern is present in each of the 20 specimens analyzed.
Chromosomal location polymorphism of major rDNA sites in two Mediterranean populations of the killifih Aphanius fasciatus (Pisces: Cyprinodontidae)
2005
The chromosomes of the Mediterranean killifish, Aphanius fasciatus from two populations, the Lagoon of Venice (LV, 15 specimens) and the Lagoon ‘Stagnone di Marsala’ (Sicily) (SM, 48 specimens), have been investigated using conventional Ag-staining and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The two methods revealed variation in the number of major rDNA sites ranging from 8 to 14 (LV) and from 1 to 4 (SM) per individual. The fact that each individual possessed its own number of sites implies that observed variation was structural. Moreover, overlapping of silver staining and FISH patterns demonstrated that all ribosomal genes were transcriptionally active in each speci…
Chromosome analysis of Bothus podas (Pisces, Pleuronectiformes) from the Mediterranean Sea
1993
A modal diploid number 2n=38 has been determined in both sexes of the pleuronectiform Bothus podas from the Gulf of Palermo (Mediterranean). An XX-XY sex-determining mechanism presumably occurs in this species. Application of silver staining (NORs) along with G- and C-banding techniques showed that secondary constrictions occurring in a large metacentric pair were variable in length in different fish. Polymorphisms of these areas seem to have a genetic, rather than transcriptional, basis.
NOR regions of polychaete worms of the genus Ophryotrocha studied by chromosome banding techniques and FISH.
2000
This article reports the results of cytogenetic analyses carried out on 10 species of polychaete worms belonging to the genus Ophryotrocha (Dorvilleidae). Nucleolar organizer regions (NORs) were characterized by Ag staining, C-banding, CMA3 staining, and ribosomal fluorescent in situ hybridization (rDNA FISH). Extensive intraspecific variation in NOR number and distribution were observed in O. costlowi, O. sp. macrovifera, O. notoglandulata, O.l. labronica, O. l. pacifica (2n = 6), O. p. puerilis, O. diadema (2n = 8), O. hartmanni, O. gracilis (2n = 10). In O. sp. robusta (2n = 10), Ag-NORs were always located on a single chromosome pair. CMA3 staining suggests a possible trend toward a GC-…
Characterization of mitotic chromosomes of four species of the genus Diplodus: Karyotypes and chromosomal nucleolar organizer region phenotypes
1996
Karyotypes have been described in four Mediterranean species of the genus Diplodus (Teleostei, Sparidae), D. vulgaris, D. puntazzo, D. sargus and D. annularis. Chromosomes were mainly acrocentric in all but D. vulgaris, where certain chromosome pairs were subtelocentric. A remarkable intraspecific heteromorphism in the number of NOR-bearing chromosomes along with a substantial interspecific variability in position of chromosomal Ag signals have been encountered. The presumed origin of multiple NOR-bearing chromosomes in Diplodus species and variation of the NOR location is discussed. ? 1996 The Fisheries Society of the British Isles