nucleolus organizer region

Summary

Summary: The chromosome region which is active in nucleolus formation and which functions in the synthesis of ribosomal RNA.

Top Publications

  1. Pontes O, Neves N, Silva M, Lewis M, Madlung A, Comai L, et al. Chromosomal locus rearrangements are a rapid response to formation of the allotetraploid Arabidopsis suecica genome. Proc Natl Acad Sci U S A. 2004;101:18240-5 pubmed
    ..Fluorescence in situ hybridization with centromere, nucleolus organizer region (NOR), and 5S rRNA gene probes reveals the expected numbers of progenitor chromosomes in natural A...
  2. Heckmann S, Schroeder Reiter E, Kumke K, Ma L, Nagaki K, Murata M, et al. Holocentric chromosomes of Luzula elegans are characterized by a longitudinal centromere groove, chromosome bending, and a terminal nucleolus organizer region. Cytogenet Genome Res. 2011;134:220-8 pubmed publisher
    ..We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability...
  3. Nguyen P, Sahara K, Yoshido A, Marec F. Evolutionary dynamics of rDNA clusters on chromosomes of moths and butterflies (Lepidoptera). Genetica. 2010;138:343-354 pubmed publisher
    ..e., homologous recombination between repetitive sequences of non-homologous chromosomes, as a primary motive force in rDNA repatterning...
  4. Fuchs J, Loidl J. Behaviour of nucleolus organizing regions (NORs) and nucleoli during mitotic and meiotic divisions in budding yeast. Chromosome Res. 2004;12:427-38 pubmed
    ..We discuss the possibility that the exclusion of the nucleolus from the spores serves the disposal of agents that resort to the nucleolus, and has a role in spore dormancy or rejuvenation...
  5. Prieto J, McStay B. Recruitment of factors linking transcription and processing of pre-rRNA to NOR chromatin is UBF-dependent and occurs independent of transcription in human cells. Genes Dev. 2007;21:2041-54 pubmed
    ..Taken together, these results highlight the importance of the specialized chromatin structure at active NORs in coordinating early events in ribosome biogenesis and nucleolar formation...
  6. Yang K, Jeong S. Genetic linkage map of the nucleolus organizer region in the soybean. Genetics. 2008;178:605-8 pubmed publisher
    Simple polymorphisms in ribosomal DNA repeats in the nucleolus organizer region (NOR) permitted the development of markers for the genetic mapping of the soybean NOR...
  7. Chattopadhyay A, Ray J. AgNOR cut-point to distinguish mild and moderate epithelial dysplasia. J Oral Pathol Med. 2008;37:78-82 pubmed publisher
    ..We demonstrated earlier that silver-stainable nucleolar organizer region (AgNOR) is a simple, inexpensive and quantifiable method which can standardize this distinction reliably...
  8. Coric M, Ladika Davidovic B, Bumber Z, Danic D, Vuletic L, Seiwerth S. Prognostic significance of DNA cytometry in combination with AgNOR investigation. Acta Otolaryngol. 2007;127:1332-7 pubmed
    ..The observed intratumoral heterogeneity could represent a possible source of conflicting and inconsistent results...
  9. Hatanaka T, Galetti P. Mapping of the 18S and 5S ribosomal RNA genes in the fish Prochilodus argenteus Agassiz, 1829 (Characiformes, Prochilodontidae). Genetica. 2004;122:239-44 pubmed
    ..Despite a lower karyotype diversification (2n = 54 and FN = 108) often observed among species of Prochilodontidae, variations involving both 45S and 5S rRNA genes could play an important role in their chromosome diversification...
  10. Shaw P, Doonan J. The nucleolus. Playing by different rules?. Cell Cycle. 2005;4:102-5 pubmed
    ..This short review describes some of the features of the nucleolus and highlights recent progress in understanding this important, but enigmatic, nuclear structure...

Detail Information

Publications62

  1. Pontes O, Neves N, Silva M, Lewis M, Madlung A, Comai L, et al. Chromosomal locus rearrangements are a rapid response to formation of the allotetraploid Arabidopsis suecica genome. Proc Natl Acad Sci U S A. 2004;101:18240-5 pubmed
    ..Fluorescence in situ hybridization with centromere, nucleolus organizer region (NOR), and 5S rRNA gene probes reveals the expected numbers of progenitor chromosomes in natural A...
  2. Heckmann S, Schroeder Reiter E, Kumke K, Ma L, Nagaki K, Murata M, et al. Holocentric chromosomes of Luzula elegans are characterized by a longitudinal centromere groove, chromosome bending, and a terminal nucleolus organizer region. Cytogenet Genome Res. 2011;134:220-8 pubmed publisher
    ..We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability...
  3. Nguyen P, Sahara K, Yoshido A, Marec F. Evolutionary dynamics of rDNA clusters on chromosomes of moths and butterflies (Lepidoptera). Genetica. 2010;138:343-354 pubmed publisher
    ..e., homologous recombination between repetitive sequences of non-homologous chromosomes, as a primary motive force in rDNA repatterning...
  4. Fuchs J, Loidl J. Behaviour of nucleolus organizing regions (NORs) and nucleoli during mitotic and meiotic divisions in budding yeast. Chromosome Res. 2004;12:427-38 pubmed
    ..We discuss the possibility that the exclusion of the nucleolus from the spores serves the disposal of agents that resort to the nucleolus, and has a role in spore dormancy or rejuvenation...
  5. Prieto J, McStay B. Recruitment of factors linking transcription and processing of pre-rRNA to NOR chromatin is UBF-dependent and occurs independent of transcription in human cells. Genes Dev. 2007;21:2041-54 pubmed
    ..Taken together, these results highlight the importance of the specialized chromatin structure at active NORs in coordinating early events in ribosome biogenesis and nucleolar formation...
  6. Yang K, Jeong S. Genetic linkage map of the nucleolus organizer region in the soybean. Genetics. 2008;178:605-8 pubmed publisher
    Simple polymorphisms in ribosomal DNA repeats in the nucleolus organizer region (NOR) permitted the development of markers for the genetic mapping of the soybean NOR...
  7. Chattopadhyay A, Ray J. AgNOR cut-point to distinguish mild and moderate epithelial dysplasia. J Oral Pathol Med. 2008;37:78-82 pubmed publisher
    ..We demonstrated earlier that silver-stainable nucleolar organizer region (AgNOR) is a simple, inexpensive and quantifiable method which can standardize this distinction reliably...
  8. Coric M, Ladika Davidovic B, Bumber Z, Danic D, Vuletic L, Seiwerth S. Prognostic significance of DNA cytometry in combination with AgNOR investigation. Acta Otolaryngol. 2007;127:1332-7 pubmed
    ..The observed intratumoral heterogeneity could represent a possible source of conflicting and inconsistent results...
  9. Hatanaka T, Galetti P. Mapping of the 18S and 5S ribosomal RNA genes in the fish Prochilodus argenteus Agassiz, 1829 (Characiformes, Prochilodontidae). Genetica. 2004;122:239-44 pubmed
    ..Despite a lower karyotype diversification (2n = 54 and FN = 108) often observed among species of Prochilodontidae, variations involving both 45S and 5S rRNA genes could play an important role in their chromosome diversification...
  10. Shaw P, Doonan J. The nucleolus. Playing by different rules?. Cell Cycle. 2005;4:102-5 pubmed
    ..This short review describes some of the features of the nucleolus and highlights recent progress in understanding this important, but enigmatic, nuclear structure...
  11. Pecinka A, Schubert V, Meister A, Kreth G, Klatte M, Lysak M, et al. Chromosome territory arrangement and homologous pairing in nuclei of Arabidopsis thaliana are predominantly random except for NOR-bearing chromosomes. Chromosoma. 2004;113:258-69 pubmed
    ..Nevertheless, in up to 31.5% of investigated Arabidopsis nuclei allelic sequences may share positions close enough for homologous recombination...
  12. Leung A, Gerlich D, Miller G, Lyon C, Lam Y, Lleres D, et al. Quantitative kinetic analysis of nucleolar breakdown and reassembly during mitosis in live human cells. J Cell Biol. 2004;166:787-800 pubmed
  13. Lewis M, Cheverud J, Pikaard C. Evidence for nucleolus organizer regions as the units of regulation in nucleolar dominance in Arabidopsis thaliana interecotype hybrids. Genetics. 2004;167:931-9 pubmed
    ..NOR2. Collectively, the data indicate that nucleolar dominance is a complex trait in which NORs, rather than individual rRNA genes, are the likely units of regulation...
  14. Adeyemi B, Kolude B, Akang E, Lawoyin J. A study of the utility of silver nucleolar organizer regions in categorization and prognosis of salivary gland tumors. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006;102:513-20 pubmed
    ..this study aimed at assessing the utility of silver nucleolar organizer region (AgNOR) staining in categorization and prognostication of salivary gland tumors...
  15. Lewis M, Pikaard D, Nasrallah M, Doelling J, Pikaard C. Locus-specific ribosomal RNA gene silencing in nucleolar dominance. PLoS ONE. 2007;2:e815 pubmed
    ..Collectively, our data suggest that rRNA gene activation can occur in a gene-autonomous fashion, independent of chromosomal location, whereas rRNA gene silencing in nucleolar dominance is locus-dependent...
  16. Bruschi D, Busin C, Siqueira S, Recco Pimentel S. Cytogenetic analysis of two species in the Phyllomedusa hypochondrialis group (Anura, Hylidae). Hereditas. 2012;149:34-40 pubmed publisher
    ..The nucleolus organizer region (NOR) was detected in pair 9 of both species, but is located in the pericentromeric region of the short ..
  17. Britton Davidian J, Cazaux B, Catalan J. Chromosomal dynamics of nucleolar organizer regions (NORs) in the house mouse: micro-evolutionary insights. Heredity (Edinb). 2012;108:68-74 pubmed publisher
    ..Such a scenario provides an alternative view from the one prevailing in most systematic and phylogenetic analyses that NORs have a high transposition rate due to concerted evolution of rRNA genes...
  18. Cabrero J, Camacho J. Location and expression of ribosomal RNA genes in grasshoppers: abundance of silent and cryptic loci. Chromosome Res. 2008;16:595-607 pubmed publisher
    ..The cryptic NORs might correspond to nascent NORs, i.e. a few rRNA gene copies moved to new locations, whereas the inactive rDNA loci might correspond to those being in the process of elimination...
  19. McStay B, Grummt I. The epigenetics of rRNA genes: from molecular to chromosome biology. Annu Rev Cell Dev Biol. 2008;24:131-57 pubmed publisher
    ..We also review the critical role of the RNA polymerase I transcription factor UBF in the formation of active nucleolar organizer regions (NORs) and maintenance of the euchromatic state of rRNA genes...
  20. Caperta A, Neves N, Viegas W, Pikaard C, Preuss S. Relationships between transcription, silver staining, and chromatin organization of nucleolar organizers in Secale cereale. Protoplasma. 2007;232:55-9 pubmed
    ..Collectively, these results suggest that rRNA gene transcription, silver staining, and NOR decondensation are interrelated in S. cereale...
  21. Hernandez Verdun D. Nucleolus: from structure to dynamics. Histochem Cell Biol. 2006;125:127-37 pubmed
    ..Time-lapse analysis of fluorescence resonance energy transfer demonstrates that processing complexes are formed in PNBs. Finally, the nucleolus appears at the center of several trafficking pathways in the nucleus...
  22. Gadbail A, Chaudhary M, Patil S, Gawande M. Actual Proliferating Index and p53 protein expression as prognostic marker in odontogenic cysts. Oral Dis. 2009;15:490-8 pubmed publisher
  23. Pillai K, Kannan S, Sujathan K, Madhavan J, Abraham E. Significance of silver-stained nucleolar organizer regions in early diagnosis and prognosis of oral squamous cell carcinoma: a multivariate analysis. In Vivo. 2005;19:807-12 pubmed
    ..Thus T3 and T4 tumours, with mean AgNOR counts more than 2.8, are aggressive and may exhibit resistance to current treatment protocols...
  24. Zhang S, Zhang H, Qin R, Jiang W, Liu D. Cadmium induction of lipid peroxidation and effects on root tip cells and antioxidant enzyme activities in Vicia faba L. Ecotoxicology. 2009;18:814-23 pubmed publisher
    ..In roots, MDA content showed an upward trend with increasing of the duration of treatment at early time and then declined...
  25. Grob A, Roussel P, Wright J, McStay B, Hernandez Verdun D, Sirri V. Involvement of SIRT7 in resumption of rDNA transcription at the exit from mitosis. J Cell Sci. 2009;122:489-98 pubmed publisher
    ..As SIRT7 activity is required to resume rDNA transcription in telophase, we propose that this conformational modification regulates onset of rDNA transcription...
  26. Nguyen T, Aniskin V, Gerbault Seureau M, Planton H, Renard J, Nguyen B, et al. Phylogenetic position of the saola (Pseudoryx nghetinhensis) inferred from cytogenetic analysis of eleven species of Bovidae. Cytogenet Genome Res. 2008;122:41-54 pubmed publisher
    ..These findings suggest that NORs are an important and frequently overlooked source of additional phylogenetic information within the Bovidae that may also have applicability at higher taxonomic levels, possibly even for Pecora...
  27. Lawrence R, Pikaard C. Chromatin turn ons and turn offs of ribosomal RNA genes. Cell Cycle. 2004;3:880-3 pubmed
    ..Independent studies using mouse and human cells have led to similar conclusions, implicating chromatin modifications as important components of the regulatory networks that control the effective dosage of active rRNA genes...
  28. Fuková I, Nguyen P, Marec F. Codling moth cytogenetics: karyotype, chromosomal location of rDNA, and molecular differentiation of sex chromosomes. Genome. 2005;48:1083-92 pubmed
    ..The demonstrated ways of W chromosome identification will facilitate the development of genetic sexing strains desirable for pest control using the sterile insect technique...
  29. Busin C, Lima A, de Almeida Prado C, Strüssmann C, Júnior S, Recco Pimentel S. Chromosomal differentiation of populations of Lysapsus limellus limellus, L. l. bolivianus, and of Lysapsus caraya (Hylinae, Hylidae). Micron. 2006;37:355-62 pubmed
    ..l. bolivianus and in pair 7 in L. caraya. These results suggest that a reassessment of the taxonomic status of L. limellus subspecies, especially of the L. l. bolivianus populations, may be necessary...
  30. Raska I, Shaw P, Cmarko D. New insights into nucleolar architecture and activity. Int Rev Cytol. 2006;255:177-235 pubmed
    ..However, the present power of light and electron microscopy (EM) techniques means that a description of nucleolar processes at the molecular level is now achievable, and the time is ripe for such an effort...
  31. Boisvert F, van Koningsbruggen S, Navascues J, Lamond A. The multifunctional nucleolus. Nat Rev Mol Cell Biol. 2007;8:574-85 pubmed
  32. Alaeddini M, Khalili M, Tirgary F, Etemad Moghadam S. Argyrophilic proteins of nucleolar organizer regions (AgNORs) in salivary gland mucoepidermoid carcinoma and its relation to histological grade. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;105:758-62 pubmed publisher
    ..The aim of this study was to assess the cellular proliferation rate of major and minor salivary gland mucoepidermoid carcinomas (MECs) by quantitative analysis of AgNOR and to determine its relation to histopathologic grading...
  33. PREUSS S, Costa Nunes P, Tucker S, Pontes O, Lawrence R, Mosher R, et al. Multimegabase silencing in nucleolar dominance involves siRNA-directed DNA methylation and specific methylcytosine-binding proteins. Mol Cell. 2008;32:673-84 pubmed publisher
  34. Trere D, Ceccarelli C, Montanaro L, Tosti E, Derenzini M. Nucleolar size and activity are related to pRb and p53 status in human breast cancer. J Histochem Cytochem. 2004;52:1601-7 pubmed
  35. Pontes O, Lawrence R, Silva M, Preuss S, Costa Nunes P, Earley K, et al. Postembryonic establishment of megabase-scale gene silencing in nucleolar dominance. PLoS ONE. 2007;2:e1157 pubmed
    ..thaliana NORs is disrupted. Collectively, these data demonstrate that HDA6 and HDT1 function in the postembryonic establishment of nucleolar dominance, a process which recurs in each generation...
  36. Mais C, Wright J, Prieto J, Raggett S, McStay B. UBF-binding site arrays form pseudo-NORs and sequester the RNA polymerase I transcription machinery. Genes Dev. 2005;19:50-64 pubmed
    ..Furthermore, we propose that UBF mediates recruitment of the pol I machinery to nucleoli independently of promoter elements...
  37. Jankun M, Ocalewicz K, Pardo B, Martinez P, Woznicki P, Sanchez L. Chromosomal characteristics of rDNA in European grayling Thymallus thymallus (Salmonidae). Genetica. 2003;119:219-24 pubmed
    ..Double variable pattern in the number and location of NORs supported the bi-directional evolution of salmonid rDNA loci...
  38. Bankfalvi A, Giuffre G, Ofner D, Diallo R, Poremba C, Buchwalow I, et al. Relationship between HER2 status and proliferation rate in breast cancer assessed by immunohistochemistry, fluorescence in situ hybridisation and standardised AgNOR analysis. Int J Oncol. 2003;23:1285-92 pubmed
    ..Moreover, in 2+ positive IHC cases, the AgNOR analysis may represent an additional tool to select patients as candidates for Herceptin therapy due to the strong negative predictor value...
  39. Guski H, Hufnagl P, Kaufmann O, Krause M, Winzer K. AgNOR analysis of atypical ductal hyperplasia and intraductal carcinoma of the breast. Anal Quant Cytol Histol. 2000;22:206-12 pubmed
    ..To determine the diagnostic and prognostic value of argyrophilic nucleolar organizer regions (AgNORs) in atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) and microinvasive ductal carcinoma (MDCA) of the breast...
  40. Sirri V, Roussel P, Hernandez Verdun D. The mitotically phosphorylated form of the transcription termination factor TTF-1 is associated with the repressed rDNA transcription machinery. J Cell Sci. 1999;112 ( Pt 19):3259-68 pubmed
    ..The reorganization of the mitotic rDNA promoter might be induced by phosphorylation of certain components of the rDNA transcription machinery and participate in silencing of rDNA during mitosis...
  41. Yue L, Iwai M, Furuta I. Evaluation of argyrophilic nucleolar organizer regions in tongue squamous cell carcinomas. Oral Oncol. 1999;35:70-6 pubmed
    ..0%), with a significant difference between the two groups (P < 0.05). The results suggest that AgNORs may reflect the degree of malignancy and cellular proliferation in tongue SCCs...
  42. Medeiros L, Rossa Feres D, Recco Pimentel S. Chromosomal differentiation of Hyla nana and Hyla sanborni (Anura, Hylidae) with a description of NOR polymorphism in H. nana. J Hered. 2003;94:149-54 pubmed
    ..However, the chromosomal morphology of both species differed from that reported for populations from other geographic regions, suggesting that a systematic reevaluation of this group of Hyla may be necessary...
  43. Roussel P, Andre C, Masson C, Geraud G, Hernandez Verdun D. Localization of the RNA polymerase I transcription factor hUBF during the cell cycle. J Cell Sci. 1993;104 ( Pt 2):327-37 pubmed
    ..The relationship between proteins associated with the NORs and ribosomal gene transcription is discussed...
  44. Piffko J, Bankfalvi A, Ofner D, Bryne M, Rasch D, Joos U, et al. Prognostic value of histobiological factors (malignancy grading and AgNOR content) assessed at the invasive tumour front of oral squamous cell carcinomas. Br J Cancer. 1997;75:1543-6 pubmed
    ..Proliferative activity, assessed by standardized AgNOR analysis, most probably represents one of the biological features underlying the usefulness of evaluating the invasive tumour front...
  45. Gébrane Younès J, Fomproix N, Hernandez Verdun D. When rDNA transcription is arrested during mitosis, UBF is still associated with non-condensed rDNA. J Cell Sci. 1997;110 ( Pt 19):2429-40 pubmed
    ..It is proposed that modifications of the transcription machinery occurring in prometaphase could explain the arrest of transcription, while reverse modifications in late anaphase could explain activation...
  46. O Sullivan A, Sullivan G, McStay B. UBF binding in vivo is not restricted to regulatory sequences within the vertebrate ribosomal DNA repeat. Mol Cell Biol. 2002;22:657-68 pubmed
    ..These results are consistent with a structural role for UBF at active nucleolar organizer regions in addition to its recognized role in stable transcription complex formation at the promoter...
  47. Savino T, Gébrane Younès J, De Mey J, Sibarita J, Hernandez Verdun D. Nucleolar assembly of the rRNA processing machinery in living cells. J Cell Biol. 2001;153:1097-110 pubmed
    ..This demonstrates the formation of one functional domain by cooperative interactions between different chromosome territories...
  48. Morais Cecilio L, Delgado M, Jones R, Viegas W. Modification of wheat rDNA loci by rye B chromosomes: a chromatin organization model. Chromosome Res. 2000;8:341-51 pubmed
    ..A model is discussed which interprets the phenotypic effects of Bs generically, in nucleotypic terms, based of their being 'genetically inert' but 'chromosomally active'...
  49. Collares Pereira M, Rab P. NOR polymorphism in the Iberian species Chondrostoma lusitanicum (Pisces: Cyprinidae)--re-examination by FISH. Genetica. 1999;105:301-3 pubmed
    ..The absence of individuals heterozygous for this polymorphism is discussed...
  50. Whitehead C, Winkfein R, Fritzler M, Rattner J. ASE-1: a novel protein of the fibrillar centres of the nucleolus and nucleolus organizer region of mitotic chromosomes. Chromosoma. 1997;106:493-502 pubmed
    ..ASE-1 co-localises with the RNA polymerase I transcription initiation factor UBF/NOR-90 throughout all stages of the cell cycle and these two proteins associate with each other in vitro...
  51. Karpen G, Schaefer J, Laird C. A Drosophila rRNA gene located in euchromatin is active in transcription and nucleolus formation. Genes Dev. 1988;2:1745-63 pubmed
    ..We conclude that 'nucleolar organizing activity' is an intrinsic property of the rDNA or its RNA products...
  52. Chan E, Imai H, Hamel J, Tan E. 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. J Exp Med. 1991;174:1239-44 pubmed
    ..Furthermore, we identified a nucleolar transcription factor as a novel target for human autoimmune response...
  53. Hasterok R, Maluszynska J. Nucleolar dominance does not occur in root tip cells of allotetraploid Brassica species. Genome. 2000;43:574-9 pubmed
  54. Sullivan G, Bridger J, Cuthbert A, Newbold R, Bickmore W, McStay B. Human acrocentric chromosomes with transcriptionally silent nucleolar organizer regions associate with nucleoli. EMBO J. 2001;20:2867-74 pubmed
    ..Incorporation of silent NORs into mature nucleoli raises interesting issues concerning the maintenance of the activity status of individual NORs...
  55. Artoni R, Bertollo L. Evolutionary aspects of the ZZ/ZW sex chromosome system in the Characidae fish, genus Triportheus. A monophyletic state and NOR location on the W chromosome. Heredity (Edinb). 2002;89:15-9 pubmed
    ..The location of rRNA genes on this chromosome may correspond to a plesiomorphic condition in the genus and, if so, predates to the sex chromosome system differentiation, with a possible influence in the initial steps of this process...
  56. Caperta A, Neves N, Morais Cecílio L, Malhó R, Viegas W. Genome restructuring in rye affects the expression, organization and disposition of homologous rDNA loci. J Cell Sci. 2002;115:2839-46 pubmed
    ..These results seem to indicate a 'sequence recognition' process for the regulation of homologous loci...
  57. Christensen M, Barthelmes H, Boege F, Mielke C. The N-terminal domain anchors human topoisomerase I at fibrillar centers of nucleoli and nucleolar organizer regions of mitotic chromosomes. J Biol Chem. 2002;277:35932-8 pubmed
    ..Thus, it provides a steady association of topoisomerase I with the rDNA and with RNA polymerase I, which is maintained in a living cell during the entire cell cycle...
  58. Ray J, Chattopadhyay A, Caplan D. Usefulness of AgNOR counts in diagnosing epithelial dysplasia. J Oral Pathol Med. 2003;32:71-6 pubmed
    ..Diagnosis of epithelial dysplasia has traditionally been subjective, and there is a need for a quantifiable and useful test...
  59. Cross I, Vega L, Rebordinos L. Nucleolar organizing regions in Crassostrea angulata: chromosomal location and polymorphism. Genetica. 2003;119:65-74 pubmed
    ..Moreover, presence of pollutants on the medium could be favoring the presence of two NORs per cell more than acting modifying expression on the NORs...
  60. Pikaard C. Nucleolar dominance: uniparental gene silencing on a multi-megabase scale in genetic hybrids. Plant Mol Biol. 2000;43:163-77 pubmed
    ..This review provides a historical perspective of nucleolar dominance research, explores the most popular hypotheses and their shortcomings, and offers some speculations concerning alternative hypotheses to be considered...
  61. Reed K, Phillips R. Polymorphism of the nucleolus organizer region (NOR) on the putative sex chromosomes of Arctic char (Salvelinus alpinus) is not sex related. Chromosome Res. 1997;5:221-7 pubmed
    Polymorphism of the nucleolus organizer region (NOR) on the putative sex chromosomes of Arctic char (Salvelinus alpinus) was examined using conventional cytogenetic and molecular techniques...
  62. Ji Y, Raska D, McKnight T, Islam Faridi M, Crane C, Zwick M, et al. Use of meiotic FISH for identification of a new monosome in Gossypium hirsutum L. Genome. 1997;40:34-40 pubmed