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GrainGenes Reference Report: CHR-100-71

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Reference	CHR-100-71
Title	Physical mapping of the 18S-5.8S-26S multigene family in common wheat: identification of a new locus.
Journal	Chromosoma
Year	1992
Volume	100
Pages	71-78
Author	Mukai Y Endo T Gill BS
Type	Article
Language	English
Abstract	In situ hybridization in conjunction with deletion mapping was used to map physically the 18S.26S multigene rRNA family in Triticum aestivum L. cv. Chinese Spring. Using in situ hybridization, we report a new locus in the 7DL arm of Chinese Spring and Aegilops squarrosa, and also confirm the nucleolus organizing region (Nor) locus in the short arm of chromosome 1A at the telomeric end in Chinese Spring. Based on in situ hybridization labeling patterns, we show that rDNA exists as condensed rDNA (heterochromatic) at each end and diffused rDNA within the secondary constriction region of the Nor-B1 (1B), Nor-B2 (6B) and Nor-D3 (5D) loci. In Nor-B1, 80% of the condensed rDNA domain lies in the proximal end and 20% in the distal end joined by diffuse rDNA threads. In Nor-B2, condensed rDNA is distributed evenly at each end joined by diffuse rDNA in the middle. In Nor-D3, the base of the satellite contains a greater concentration of condensed rDNA than the tip of the short arm. On the basis of these observations, we support the model that the usual state of rDNA is inactive (facultatively heterochromatic; Hilliker and Appels 1989). A small fraction of rDNA at a specific location (usually in the middle in wheat) exists as a diffuse region (active) in condensed chromosomes
Keyword	[ Hide all but 1 of 8 ] C bands deletions DNA DNA hybridization loci nucleolus ribosomal RNA Triticum aestivum
Agricola Code	IND91022373
Gene Catalogue Number	740
Cited in	McIntosh RA et al. (1995) Catalogue of gene symbols for wheat. Proceedings of the 8th International Wheat Genetics Symposium 1333-1500.

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