Nucleolar organizer region
The nucleolus organizer region (NOR) or nucleolar organizer is a chromosomal region around which the nucleolus forms. This region is the particular part of a chromosome that is associated with a nucleolus after the nucleus divides. The region contains several tandem copies of ribosomal DNA genes. In humans, the NOR contains genes for 5.8S, 18S, and 28S rRNA clustered on the short arms of chromosomes 13, 14, 15, 21 and 22 (the acrocentric chromosomes).
Nucleolus organizer regions (NORs) are head-to-tail arrays of genes encoding the precursor of the three largest ribosomal RNAs (18S, 5.8S and 25S in plants). NORs include active rRNA genes, which give rise to secondary constrictions of metaphase chromosomes, and silent rRNA genes, which are often highly compacted in dense heterochromatin. At metaphase, a proteinaceous remnant of the nucleolus often remains associated with the secondary constriction. Each rRNA gene at a NOR is nearly identical in sequence, although variation in size due to differences in the number of repeated DNA elements in the intergenic spacer region is common.
In complete chromosome complements there were always 6 chromosomes with a terminal Nucleolus organizing region (NOR). In most cases part of the NOR was decondensed, and several of this decondensed areas formed together a big collecting nucleolus (ger. Sammlenukleolus). This collecting nucleolus was easily visible in phase contrast even without pretreatment due to its large size and particular structure. The shape of the collecting nucleolus ranged from nearly circular to irregular. Instead of just one collecting nucleolus of 6 NOR there were also several smaller collecting nucleoli made up from the NORs of only 2 to 5 nucleolus organizing chromosomes.
Evaluation of nucleolar organizer region-associated proteins in breast malignancy. Nucleolus organizer regions (NORs) have been identified by means of an argyrophilic technique (Ag-NOR) in routinely processed, formalin-fixed paraffin sections of breast lesions. This method reveals NORs as black dots in the nuclei of cells, by virtue of the argyrophilia of NOR-associated proteins. The number of Ag-NORs has been thought to be related to cellular activation and has recently been applied to non-Hodgkin’s lymphomas and melanocytic skin lesions. It was found in the present study that the total number of Ag-NORs in malignant breast lesions significantly exceeded those of normal breast and benign lesions. The number of clumps of Ag-NORs, however, were not useful discriminators. Neither numbers of total Ag-NORs nor of clumps of Ag-NORs correlate with mitotic counts and it may be that their numbers relate to ploidy. It is suggested that the Ag-NOR technique will find increasing application as an adjunct to diagnostic histopathology.
In karyotype analysis, a silver stain can be used to identify the NOR.Silver nitrate inserts into the NOR-associated protein in the stalks and satellites, staining the proteins dark black. The amount of stain deposited and the number of NORs differs among the population, although the cell should normally have a maximum of 10 NORs per cell.
Several genes are located at the NOR, including RUNX2,UBTF, and APC genes.

This is an excerpt from the article Nucleolar organizer region from the Wikipedia free encyclopedia. A list of authors is available at Wikipedia.
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Nucleolus organizer region - Wikipedia, the free encyclopedia
The nucleolus organizer region (NOR) or nucleolar organizer is a chromosomal region around which the nucleolus forms. This region is the particular part of a ...
en.wikipedia.org/wiki/Nucleolus_organizer_region
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Nucleolus organizer region - The Free Dictionary
Noun, 1. nucleolar organizer - the particular part of a chromosome that is associated with a nucleolus after nuclear division. nucleolar organiser, nucleolus ...
www.thefreedictionary.com/Nucleolus+organizer+region
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nucleolus organizer region - Medical Dictionary - The Free Dictionary
nu·cle·o·lus or·ga·niz·er re·gion. an arrangement of the DNA coding for the production of ribosomal RNA (rRNA). Want to thank TFD for its existence? Tell a friend ...
medical-dictionary.thefreedictionary.com/nucleolus+organizer+region
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GO:0005731 nucleolus organizer region
Name, nucleolus organizer region. Ontology, Cellular Component. Definition, A region of a chromosome where nucleoli form during interphase, and where ...
www.ebi.ac.uk/QuickGO/GTerm?id=go:0005731
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Molecular and biochemical aspects of interphase nucleolar ...
Controlled silver-staining of nucleolus organizer regions with a protective ... Correlation between DNA flow cytometric and Nucleolar organizer region data in ...
www.ncbi.nlm.nih.gov/pmc/articles/PMC408010/
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Behaviour of nucleolus organizing regions (NORs) and nucleoli ...
Behaviour of nucleolus organizing regions (NORs) and nucleoli during mitotic and meiotic divisions in budding yeast. Fuchs J, Loidl J. Institute of Botany ...
www.ncbi.nlm.nih.gov/pubmed/15252239
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On the position of nucleolus organizer regions (NORs) in interphase ...
The distribution of 18S and 28S ribosomal RNA (rRNA), i.e. the chromosomal nucleolus organizer regions (NORs) was visualized in interphases and ...
www.ncbi.nlm.nih.gov/pubmed/3758203
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Heredity - Chromosomal dynamics of nucleolar organizer regions ...
Nov 16, 2011 ... Nucleolar organizer regions (NORs) are chromosomal landmarks that consist of tandemly repeated sequences of ribosomal genes (rRNA).
www.nature.com/hdy/journal/v108/n1/full/hdy2011105a.html
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Nucleolus Organizer Region (definition) - Reference.MD
Definition: The chromosome region which is active in nucleolus formation and which functions in the synthesis of ribosomal RNA. Other names Nucleolar ...
www.reference.md/files/D009/mD009697.html
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Improvements in the Silver-staining Technique for Nucleolar ...
The Nucleolar organizer regions (NORs) found on human chro- mosomes 13,14, 15,21, and 22 (5,9,20) are the sites of the transcrip- tion of ribosomal RNA, the ...
jhc.sagepub.com/content/41/3/439.full.pdf
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Nucleolar organizer region in science
Morphometric evaluation of argyrophilic nucleolar organizer region ...
Department of Pathology, Faculty of Medicine, University of São Paulo, Brazil. Nucleolar organizer regions identified by means of an argyrophilic technique ...
Demonstration of silver-stained nucleolar organizer region ...
Gerhard-Domagk-Institute of Pathology, University of Münster, Germany. Argyrophilic Nucleolar organizer region associated proteins (AgNORs) are known to ...
Silver-binding nucleolar organizer regions (AgNORs) in bronchial ...
Silver-binding Nucleolar organizer regions (AgNORs) in bronchial tumors. ... of Pathophysiology, Medical School of the Jagiellonian University, KrakĂłw, Poland.
Estimation of Silver-Binding Nucleolar Organizer Regions (AgNORs ...
We quantified Nucleolar organizer regions demonstrable by silver staining technique ... Department of Oral Pathology, Nagasaki University School of Dentistry, ...
Heredity - Abstract of article: Loss of nucleolar-organizer regions ...
3Current address: Department of Botany, University of Reading, Whiteknights, ... The organization and behaviour of nucleolar-organizer regions (NOR) of Scilla ...
Spectrum of argyrophilic nucleolar organizer region (AgNOR ...
May 6, 2013 ... Nikicicz EP, Norback D. "Spectrum of argyrophilic Nucleolar organizer region ( AgNOR) staining patterns in chronic and transformed B-cell ...
Morphometric Evaluation of Argyrophilic Nucleolar Organizer ...
Morphometric Evaluation of Argyrophilic Nucleolar organizer region Is Useful in ... Nucleolar organizer regions identified by means of an argyrophilic technique ...
[PDF]Argyrophilic nucleolar organiser region (AgNOR) - Journal of ...
University of. Wisconsin, Madison, and the ... Nucleolar organiser regions (NORs) are loops of chromosomal DNA ... method for argyrophilic nucleolar organiser.
[PDF]Improvements in the Silver-staining Technique for Nucleolar ...
The Nucleolar organizer regions (NORs) found on human chro- mosomes 13,14, 15,21, and 22 (5,9 ... Texas A&M University, College Station, TX 77843-1114.
Amazon.com: Silver staining of rabbit nucleolus organizer regions ...
Silver staining of rabbit nucleolus organizer regions: Discovery of pericentric inversions (University of Hawaii) [Michael James Macera] on Amazon.com. * FREE* ...
Books on the term Nucleolar organizer region
Genetics Manuals: Current Theory, Concepts, Terms
Genetics Manuals: Current Theory, Concepts, Terms
G. P. Rédei, 1998
NUCLEOLUS Nucleolar organizer continued Nucleolar organizer region MAIZE CHROMOSOME 6 Morphologically the nucleolar organizing regions (NOR) are identified by secondary constrictions. The number of nucleolar  ...
Plant Cell Biology: Structure and Function
Plant Cell Biology: Structure and Function
Brian E. S. Gunning, Martin William Steer, 1996
Micrograph (b) shows a trailing chromosome arm possessing a Nucleolar organizer region (NO), and a further example of the same structure is included in (c). Spindle microtubules (MT) are seen in (b). Note also the vesicles (VE) amongst the ...
Marsupial Genetics and Genomics
Marsupial Genetics and Genomics
Janine E. Deakin, Paul Damian Waters, Jennifer A. Marshall Graves, 2010
Surprisingly, marsupial sex chromosomes have no homologous pseudo- autosomal region, although the X and the Y chromosome may share heterochro- matic ... 8.3.4. Nucleolus. Organizer. Region. (NOR). Some marsupial species have ...
Methods in Disease: Investigating the Gastrointestinal Tract
Methods in Disease: Investigating the Gastrointestinal Tract
Victor R. Preedy, Ronald R. Watson, 1998
Ploton D, Meneger M, Jeannesson P, Himber G, Pigeon F, Adnej J. Improvement in the staining and visualization of the argyrophilic proteins of Nucleolar organizer region at the optical level. HistochemJ 1986; 18:5-14. 2. RuschoffJ, Plate K ...
Encyclopedia of Genetics, Genomics, Proteomics, and Informatics
Encyclopedia of Genetics, Genomics, Proteomics, and Informatics
George P. Rédei, 2008
Nucleolar Organizer: The location of the highly repeated genes responsible for coding ribosomal RNA. It also assembles the products of their transcription until utilization. Morphologically, the nucleolar-organizing regions (NOR) are identified  ...
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Blog posts on the term
Nucleolar organizer region
A case-control study of oral epithelial proliferative markers among Sudanese Toombak dippers using micronuclei assay, argyrophilic nucleolar organizer region, Papanicolaou and crystal violet methods | Abbas | Rare Tumors
A case-control study of oral epithelial proliferative markers among Sudanese Toombak dippers using micronuclei assay, argyrophilic Nucleolar organizer region, Papanicolaou and crystal violet methods
www.pagepress.org/journals/index.php/rt/article/view/rt.2013.e31
Observations of Nucleolar Organizer Regions in Benign and Malignant Breast Lesions | STMPAPERS.com
www.stmpapers.com/observations-of-nucleolar-organizer-regions-in-benign-and-malignant-breast-lesions/
Nucleolar Organizer (Molecular Biology)
Nucleolar organizers are secondary constrictions within the mitotic chromosomes of eukaryotes. The primary constriction occurs at the centromere. The nucleolar organizer genetic locus contains tandemly repeated genes that encode the 42 S to 47 S precursor of ribosomal RNA (pre-rRNA)
what-when-how.com/molecular-biology/nucleolar-organizer-molecular-biology/
Diagnostic Pathology | Full text | Long-term analysis to objectify the tumour grading by means of automated microscopic image analysis of the nucleolar organizer regions (AgNORs) in the case of breast carcinoma
Apart from a number of cases of inaccurate prognosis in regard to individual patients, the inter- and intra-observer variability of the classical, histological prognosis parameters have been under repeated discussion. For this reason, a long-term analysis was carried out in regard to overall survival by means of automated microscopic image analysis of the Nucleolar organizer regions (AgNORs) to objectify tumour grading in the case of breast carcinoma.
www.diagnosticpathology.org/content/8/1/56
theagricos.com | Structure of Chromosome
Chromosome Structure,Chromatid,Chromonema,Primary constriction,Centromere,Kinetochore,Telomers,Secondary Constriction,Nucleolar Organizer,Satellite,Chromomeres, are given
theagricos.com/genetics/chromosome/chromosome-structure/
PLOS ONE: Elucidation of Motifs in Ribosomal Protein S9 That Mediate Its Nucleolar Localization and Binding to NPM1/Nucleophosmin
PLOS ONE: an inclusive, peer-reviewed, open-access resource from the PUBLIC LIBRARY OF SCIENCE. Reports of well-performed scientific studies from all disciplines freely available to the whole world.
www.plosone.org/article/info:doi/10.1371/journal.pone.0052476
Nucleolus ~ Biology Exams 4 U
A biology exam preparation portal
www.biologyexams4u.com/2012/06/nucleolus.html
Structure and Epigenetics of Nucleoli in Comparison With Non-nucleolar Compartments
jhc.sagepub.com/content/58/5/391.short
Plant Life: Nucleolus
Nucleolus The most prominent organelle of the eukaryotic cell is the nucleus. Within the nucleus, substructures called nucleoli are visible by light microscopy, each nucleolus as a small spot.
lifeofplant.blogspot.com/2011/03/nucleolus.html
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