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Title: GC- rich heterochromatin in silver stained nucleolar organizer regions (NORs) fluoresces with Chromomycin A3 (CMA3) staining in three species of teleostean fishes (Pisces)
Authors: Das, Jayanta Kumar
Khuda-Bukhsh, Anisur Rahman
Keywords: Ag-NOR;Chromomycin A3 banding;Chromomycin A3 banding;G-C rich region;Hemibagrus menoda;Karyotype;Mastacembelus armatus;Sperata seenghala
Issue Date: May-2007
Publisher: CSIR
Abstract: In a bid to ascertain the molecular architecture of the silver positive regions (NORs) in chromosomes of three species of fish, namely, Hemibagrus menoda (Hamilton), Sperata seenghala (Sykes) (Fam: Bagridae) and Mastacembelus armatus (Lacep├Ęde) (Fam: Mastacembelidae), an additional staining methodology using a fluorochrome dye (Chromomycin A3) was deployed along with the AgNO3 technique. The nucleolar organizing regions (NORs) were located terminally at the shorter arms (Tp) of one pair of submetacentric chromosomes (No.3) in H. menoda (2n=58), at the longer arms (Tq) of one pair of submetacentric chromosomes (No.5) in S. seenghala (2n=50) and at the shorter arm (Tp) of one pair of homologous submetacentric chromosomes (No.6) in M. armatus (2n=48). Staining with Chromomycin A3 produced bright fluorescing zones in GC- rich heterochromatin of Ag-positive NORs. The results indicate a more general trend of existence of an overlapping region between NOR and GC- rich fluorescing zones, the active sites of rRNA genes (rDNA) in this primitive group of vertebrates although exceptions to this situation has been reported in a couple of extant fish species earlier. More data utilizing such combined methodologies are warranted to understand the structural organization of fish chromosomes more precisely.
Page(s): 413-418
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Appears in Collections:IJEB Vol.45(05) [May 2007]

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