Nucleolus 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 RNA genes.[1] 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).

In karyotype analysis, a silver stain can be used to identify the NOR.[2][3] 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,[4] UBTF,[5] and APC[6] genes.



Barbara McClintock first described the "nucleolar-organizing body" in Zea mays in 1934.[7][8]

See also


  1. ^ "Counting the Nucleolar Organizer Region—Associated Proteins Is a Prognostic Clue of Malignant Melanoma" - Archives of Dermatology
  2. ^ Bloom SE, Goodpasture C. (1976). "An improved technique for selective silver staining of Nucleolar Organizer Regions in human chromosomes". Human Genetics 34 (2): 199–206. doi:10.1007/BF00278889. PMID 63440. 
  3. ^ Lay YF, Pfeiffer RA, Arrighi FE, Hsa TC (1978). "Combination of silver and fluorescent staining for metaphase chromosomes". American Journal of Human Genetics 30 (1): 76–79. PMC 1685453. PMID 74950. 
  4. ^ Young DW, Hassan MQ, Pratap J, Galindo M, Zaidi SK, Lee S, Yang X, Xie R, Javed A, Underwood JM, Furcinitti P, Imbalzano AN, Penman S, Nickerson JA, Montecino MA, Lian JB, Stein JL, van Wijnen AJ, Stein GS (2007). "Mitotic occupancy and lineage-specific transcriptional control of rRNA genes by Runx2". Nature 445 (7126): 442–446. doi:10.1038/nature05473. PMID 17251981. 
  5. ^ Chan EKL, Imai H, Hamel JC, Tan EM (1991). "Human autoantibody to RNA polymerase I transcription factor hUBF: molecular identity of nucleolus organizer region autoantigen NOR-90 and ribosomal RNA transcription upstream binding factor". Journal of Experimental Medicine 174 (5): 1239–1244. doi:10.1084/jem.174.5.1239. PMC 2119007. PMID 1940801. 
  6. ^ Tischfield JA, Shao C (2003). "Somatic recombination redux". Nature Genetics 33 (1): 5–6. doi:10.1038/ng0103-5. PMID 12509771. 
  7. ^ McClintock B (1934). "The relation of a particular chromosomal element to the development of the nucleoli in Zea mays". Zeitschrift fur Zellforschung und mikroskopische Anatomie 21 (2): 294–328. doi:10.1007/BF00374060. 
  8. ^ "Dr. Barbara McClintock, 90, Gene Research Pioneer, Dies" - New York Times

External links

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