scholarly journals Chromosome Dynamics Regulating Genomic Dispersion and Alteration of Nucleolus Organizer Regions (NORs)

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 971
Author(s):  
Hirohisa Hirai
Keyword(s):  
Transcriptional Activity ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Dispersion Systems ◽  
Rdna Loci ◽  
Silver Nitrate Staining ◽  
Staining Methods ◽  
Acrocentric Chromosomes ◽  
Reciprocal Associations

The nucleolus organizer regions (NORs) demonstrate differences in genomic dispersion and transcriptional activity among all organisms. I postulate that such differences stem from distinct genomic structures and their interactions from chromosome observations using fluorescence in situ hybridization and silver nitrate staining methods. Examples in primates and Australian bulldog ants indicate that chromosomal features indeed play a significant role in determining the properties of NORs. In primates, rDNA arrays that are located on the short arm of acrocentrics frequently form reciprocal associations (“affinity”), but they lack such associations (“non-affinity”) with other repeat arrays—a binary molecular effect. These “rules” of affinity vs. non-affinity are extrapolated from the chromosomal configurations of meiotic prophase. In bulldog ants, genomic dispersions of rDNA loci expand much more widely following an increase in the number of acrocentric chromosomes formed by centric fission. Affinity appears to be a significantly greater force: associations likely form among rDNA and heterochromatin arrays of acrocentrics—thus, more acrocentrics bring about more rDNA loci. The specific interactions among NOR-related genome structures remain unclear and require further investigation. Here, I propose that there are limited and non-limited genomic dispersion systems that result from genomic affinity rules, inducing specific chromosomal configurations that are related to NORs.

scholarly journals First cytogenetic analysis of lesser gymnures (Mammalia, Galericidae, Hylomys) from Vietnam

2018 ◽  
Vol 12 (3) ◽  
pp. 361-372 ◽  
Author(s):  
Svetlana V. Pavlova ◽  
Larisa S. Biltueva ◽  
Svetlana A. Romanenko ◽  
Natalya A. Lemskaya ◽  
Anton V. Shchinov ◽  
...  
Keyword(s):  
Taxonomic Status ◽  
Genetic Distances ◽  
Nucleolus Organizer ◽  
Telomeric Dna ◽  
Dapi Staining ◽  
Nucleolus Organizer Regions ◽  
Southern Vietnam ◽  
Acrocentric Chromosomes ◽  
First Time

Gymnures are an ancient group of small insectivorous mammals and are characterized by a controversial taxonomic status and the lack of a description of karyotypes for certain species. In this study, conventional cytogenetic techniques (Giemsa, CBG- and GTG-banding, Ag-NOR), CMA3-DAPI staining, and fluorescent in situ hybridization (FISH) with telomeric DNA probes were used to examine for the first time the karyotypes of lesser gymnures of group Hylomyssuillus Müller, 1840 from northern and southern Vietnam. All studied specimens had karyotypes with 2n=48, NFa=64. C-positive heterochromatic blocks existed in centromeric regions of 7 bi-armed autosomes and the submetacentric X chromosome. The Y chromosome is a C-positive and dot-like. The nucleolus organizer regions resided terminally on the short arms of 2 small bi-armed pairs. Positive signals at the telomeres of all chromosomes were revealed by FISH. CMA3-positive blocks were localized on the telomeric and pericentric regions of most bi-armed and acrocentric chromosomes. Despite the large genetic distances between Hylomys Müller, 1840, lesser gymnures from H.suillus-group from northern and southern Vietnam have similar karyotypic characteristics.

scholarly journals Karyotype and chromosomal characteristics of rDNA of Cobitis strumicae Karaman, 1955 (Teleostei, Cobitidae) from Lake Volvi, Greece

2018 ◽  
Vol 12 (4) ◽  
pp. 483-491 ◽  
Author(s):  
Eva Hnátková ◽  
Costas Triantaphyllidis ◽  
Catherine Ozouf-Costaz ◽  
Lukáš Choleva ◽  
Zuzana Majtánová ◽  
...  
Keyword(s):  
Chromosome Pair ◽  
Nucleolus Organizer ◽  
Telomeric Region ◽  
Submetacentric Chromosome ◽  
Rdna Probe ◽  
Nucleolus Organizer Regions ◽  
Heteromorphic Sex Chromosomes ◽  
Acrocentric Chromosomes ◽  
Phylogenetic Lineages

The karyotype of Greek cobitid fish Cobitisstrumicae Karaman, 1955, from Lake Volvi, Greece, a representative of one of its two major intraspecific phylogenetic lineages, was analysed by means of sequential Giemsa-staining, C-banding, silver-staining, CMA3 fluorescence banding and also by in situ hybridization (FISH) with rDNA probe. The diploid chromosome number was 2n = 50, karyotype composed of 10 pairs of metacentric to submetacentric and 15 pairs of subtelocentric to acrocentric chromosomes. The nucleolus organizer regions (NORs) as revealed by Ag- and CMA3 staining and FISH were situated in the telomeric region of the fourth submetacentric chromosome pair. The chromosomes contained very low content of C-positive heterochromatin. No heteromorphic sex chromosomes were detected. This first karyotype report for any species of lineage Bicanestrinia Băcescu, 1962 shows a simple karyotype dominated by acrocentric chromosomes and possessing single NOR-bearing chromosome pair. Cytotaxonomic implications of this finding for the taxonomy of the genus Cobitis Linnaeus, 1758 are further discussed.

The banded chromosomes of the muskox (Ovibos moschatus)

1989 ◽  
Vol 67 (5) ◽  
pp. 1155-1158 ◽  
Author(s):  
Daniel M. Desaulniers ◽  
W. A. King ◽  
Janice E. Rowell ◽  
Peter F. Flood
Keyword(s):  
Silver Nitrate ◽  
X Chromosome ◽  
Water Buffalo ◽  
Nucleolus Organizer ◽  
Rrna Genes ◽  
Ovibos Moschatus ◽  
Nucleolus Organizer Regions ◽  
The Family ◽  
Silver Nitrate Staining ◽  
Acrocentric Chromosomes

The muskox (Ovibos moschatus), a member of the family Bovidae, has 48 chromosomes consisting of 12 biarmed and 34 acrocentric autosomes, an acrocentric X chromosome, and a small metacentric Y chromosome. To obtain more information about this species, chromosome preparations from cultured lymphocytes were R-banded, C-banded, or stained with silver nitrate. R-banding was sufficient to identify individual chromosomes. C-banding revealed prominent centromeric bands on all acrocentric chromosomes and very faint staining of the centromeric regions of the biarmed chromosomes. This pattern has been observed in other bovids, such as sheep and water buffalo, which also have biarmed and acrocentric chromosomes. Silver nitrate staining revealed a per metaphase average of 5.23 nucleolus organizer regions, the chromosomal sites of rRNA genes. The nucleolus organizer regions were located on the ends of the long arm of three pairs of submetacentric and two pairs of acrocentric autosomes. Similar numbers of terminally located nucleolus organizer regions have been observed in other bovids such as cattle, sheep, and goats. These results parallel those obtained in other members of the family and emphasize the general cytogenetic similarity within the Bovidae.

scholarly journals Ultrastructural cytochemistry of the mammalian cell nucleolus.

1990 ◽  
Vol 38 (9) ◽  
pp. 1237-1256 ◽  
Author(s):  
M Derenzini ◽  
M Thiry ◽  
G Goessens
Keyword(s):  
Structure Function ◽  
Mammalian Cell ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
The Past ◽  
Nucleolar Chromatin ◽  
Function Relationship ◽  
Relationship Of ◽  
Nucleolar Components

In the present review on the organization of the mammalian cell nucleolus, we report and discuss data obtained during the past 10 years by means of cytochemical and immunocytochemical ultrastructural techniques. Particular emphasis is placed on the following topics: location of the nucleolus organizer regions in interphasic nucleolar components, structure of nucleolar chromatin in situ, and the structure-function relationship of the nucleolar components. The cytochemical and immunocytochemical results are compared and the concordant data are stressed for each topic.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VI. Production and identification of primary trisomics using the C-banding technique

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 542-555 ◽  
Author(s):  
B. Friebe ◽  
N.-S. Kim ◽  
J. Kuspira ◽  
B. S. Gill
Keyword(s):  
Nucleolus Organizer ◽  
Triticum Monococcum ◽  
Banding Patterns ◽  
Primary Trisomics ◽  
Nucleolus Organizer Regions ◽  
C Banding ◽  
A Genome ◽  
Chromosome 5A ◽  
Triple Dose

Cytogenetic studies in Triticum monococcum (2n = 2x = 14) are nonexistent. To initiate such investigations in this species, a series of primary trisomics was generated from autotriploids derived from crosses between induced autotetraploids and diploids. All trisomics differed phenotypically from their diploid progenitors. Only two of the seven possible primary trisomic types produced distinct morphological features on the basis of which they could be distinguished. The chromosomes in the karyotype were morphologically very similar and could not be unequivocally identified using standard techniques. Therefore, C-banding was used to identify the chromosomes and trisomics of this species. Ag–NOR staining and in situ hybridization, using rDNA probes, were used to substantiate these identifications. A comparison of the C-banding patterns of the chromosomes of T. monococcum with those of the A genome in Triticum aestivum permitted identification of five of its chromosomes, viz., 1A, 2A, 3A, 5A, and 7A. The two remaining chromosomes possessed C-banding patterns that were not equivalent to those of any of the chromosomes in the A genome of the polyploid wheats. When one of these undesignated chromosomes from T. monococcum var. boeoticum was substituted for chromosome 4A of Triticum turgidum, it compensated well phenotypically and therefore genetically for the loss of this chromosome in the recipient species. Because this T. monococcum chromosome appeared to be homoeologous to the group 4 chromosomes of polyploid wheats, it was designated 4A. By the process of elimination the second undesignated chromosome in T. monococcum must be 6A. Analysis of the trisomics obtained led to the following conclusions. (i) Trisomics for chromosome 3A were not found among the trisomic lines analyzed cytologically. (ii) Primary trisomics for chromosomes 2A, 4A, 6A, and 7A were positively identified. (iii) Trisomics for the SAT chromosomes 1A and 5A were positively identified in some cases and not in others because of polymorphism in the telomeric C-band of the short arm of chromosome 1A. (iv) Trisomics for chromosome 7A were identified on the basis of their distinct phenotype, viz., the small narrow heads and small narrow leaves. Because rRNA hybridizes lightly to nucleolus organizer regions on chromosome 1A and heavily to nucleolus organizer regions on chromosome 5A, our results indicate that trisomics in line 50 carry chromosome 1A in triple dose and trisomics in lines 28 and 51 carry chromosome 5A in triplicate. Variable hybridization of the rDNA probe to nucleolus organizer regions on chromosomes in triple dose in lines 7, 20, and 28 precluded the identification of the extra chromosome in these lines. Cytogenetic methods for unequivocally identifying trisomics for chromosomes 1A and 5A are discussed. Thus six of the series of primary trisomics have been identified. Telotrisomic lines are also being produced.Key words: Triticum monococcum, trisomics, C-banding, Ag-NOR staining, in situ hybridization, rDNA probes, plant morphology.

Frequency of Ag-stained nucleolus organizer regions in the acrocentric chromosomes of man

1977 ◽  
Vol 37 (1) ◽  
pp. 73-77 ◽  
Author(s):  
A. V. Mikelsaar ◽  
M. Schmid ◽  
W. Krone ◽  
H. G. Schwarzacher ◽  
W. Schnedl
Keyword(s):  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Acrocentric Chromosomes

Chromosomal Localization of 18S-28S rDNA and (TTAGGG)n Sequences in Two South African Dormice of the Genus Graphiurus (Rodentia: Gliridae)

2019 ◽  
Vol 158 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Vanessa Milioto ◽  
Sara Vlah ◽  
Sofia Mazzoleni ◽  
Michail Rovatsos ◽  
Francesca Dumas
Keyword(s):  
South African ◽  
Evolutionary Dynamics ◽  
Repetitive Sequences ◽  
Nucleolus Organizer ◽  
28S Rdna ◽  
Telomeric Sequences ◽  
Nucleolus Organizer Regions ◽  
Interstitial Telomeric Sequences ◽  
Almost All

Classical cytogenetics and mapping of 18S-28S rDNA and (TTAGGG)n sequences by fluorescence in situ hybridization (FISH) was performed on Graphiurus platyops (GPL) and Graphiurus ocularis (GOC) metaphases with the aim to characterize the genomes. In both species, inverted DAPI karyotypes showed the same diploid number, 2n = 46, and hybridization of the (TTAGGG)n probe revealed interstitial telomeric sequences (ITSs) at the centromeres of almost all bi-armed chromosomes. FISH with the rDNA probe localized nucleolus organizer regions (NORs), at the terminal ends of the p arms of the subtelocentric pairs 16 and 17 in both species and detected additional signals on GPL8 and GOC18, 19, and 22. The species have similar karyotypes, but their chromosome pairs 18-22 differ in morphology; these are acrocentric in G. platyops, as also confirmed by C-banding, and subtelocentric in G. ocularis. These differences in pairs 18-22 were also highlighted by hybridization of the telomeric probe (TTAGGG)n, which showed the small p arms in G. ocularis enriched with ITSs. FISH of rDNA probes detected multiple NOR loci in G. ocularis, underlining the intense evolutionary dynamics related to these genes. Although the Graphiurus species analyzed have similar karyotypes, the results on the repetitive sequences indicate a complex pattern of genomic reorganization and evolution occurring in these phylogenetically close species.

scholarly journals Comparative cytogenetic of six species of Amazonian Peacock bass (Cichla, Cichlinae): intrachromosomal variations and genetic introgression among sympatric species

2020 ◽  
Vol 14 (3) ◽  
pp. 437-451
Author(s):  
Janice Quadros ◽  
Alex M. V. Ferreira ◽  
Patrik F. Viana ◽  
Leandro Marajó ◽  
Ezequiel Oliveira ◽  
...  
Keyword(s):  
Morphological Characteristics ◽  
5S Rdna ◽  
Heterochromatic Region ◽  
Sympatric Species ◽  
Nucleolus Organizer ◽  
Genetic Introgression ◽  
Nucleolus Organizer Regions ◽  
River Region ◽  
Cytogenetic Analyses ◽  
Acrocentric Chromosomes

Cytogenetic data for the genus Cichla Bloch et Schneider, 1801 are still very limited, with only four karyotype descriptions to date. The sum of the available cytogenetic information for Cichla species, points to a maintenance of the diploid number of 48 acrocentric chromosomes, considered a typical ancestral feature in cichlids. In the current study, we performed molecular and classical cytogenetic analyses of the karyotype organization of six species of Cichla, the earliest-diverging genus of Neotropical cichlids. We cytogenetically analysed Cichla kelberi Kullander et Ferreira, 2006, Cichla monoculus Agassiz, 1831, Cichla piquiti Kullander et Ferreira, 2006, Cichla temensis Humboldt, 1821, Cichla vazzoleri Kullander et Ferreira, 2006 and Cichla pinima Kullander et Ferreira, 2006, including three individuals that showed mixed morphological characteristics, likely from different species, suggesting they were hybrid individuals. All individuals analysed showed 2n = 48 acrocentric chromosomes, with centromeric heterochromatic blocks on all chromosomes and a terminal heterochromatic region on the q arm of the 2nd pair. Mapping 18S rDNA gave hybridization signals, correlated with the nucleolus organizer regions, on the 2nd pair for all analyzed individuals. However, we found distinct patterns for 5S rDNA: interstitially at the proximal position on 6th pair of four species (C. kelberi, C. pinima, C. piquiti and C. vazzoleri), and on the distal of the 4th pair in two (C. monoculus and C. temensis). Accordingly, we present here new data for the genus and discuss the evolutionary trends in the karyotype of this group of fish. In addition, we provide data that supports the occurrence of hybrid individuals in the Uatumã River region, mainly based on 5S rDNA mapping.

scholarly journals A combined AgNOR-Feulgen staining technique.

1990 ◽  
Vol 38 (11) ◽  
pp. 1591-1597 ◽  
Author(s):  
J Foucrier ◽  
J P Rigaut ◽  
D Pechinot
Keyword(s):  
Transcriptional Activity ◽  
Staining Method ◽  
Staining Technique ◽  
Nucleolus Organizer ◽  
Optimal Conditions ◽  
Feulgen Staining ◽  
Rdna Genes ◽  
Nucleolus Organizer Regions ◽  
Agnor Staining

We describe a new staining technique (H-Ag-S) which allows observation and counting of active nucleolus organizer regions (NORs) and evaluation of the amount of DNA in the same cell nucleus. The procedure consists of combining a modified AgNOR staining method with the Feulgen reaction. A sequential procedure is proposed, based on the determination of optimal staining conditions. The technique, which was designed to allow studies of correlations between the transcriptional activity of rDNA genes and the cell ploidy, was primarily developed for rat liver smears. It should be applicable to most biological preparations, but the optimal conditions might be variable.

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