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GrainGenes Reference Report: CHR-110-24

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Reference	CHR-110-24
Title	A tandemly repeated DNA sequence is associated with both knob-like heterochromatin and a highly decondensed structure in the meiotic pachytene chromosomes of rice
Journal	Chromosoma
Year	2001
Volume	110
Pages	24-31
Author	Cheng Z Stupar RM Gu M Jiang J
Abstract	Summary: Highly repetitive tandem DNA sequence repeats are often associated with centromeric and telomeric regions of eukaryotic chromosomes. The rice tandem repeat Os48 is organized as long arrays of a 355 bp monomer and is mainly located in the telomeric regions. The chromosomal locations of the Os48 sequence were determined by fluorescence in situ hybridization (FISH) on rice pachytene chromosomes. The majority of the Os48 loci are associated with brightly 4',6-diamidino-2-phenylindole (DAPI)-stained and knob-like heterochromatin in rice pachytene chromosomes. As with other DNA sequences located in the heterochromatic regions, the cytosines of the CG and C(A/T)G sites within the Os48 repeat are heavily methylated. Surprisingly, a proportion of the FISH signals are highly decondensed and deviate significantly from the DAPI-stained periphery of the pachytene chromosomes. This highly decondensed chromatin structure has not been reported in pachytene chromosomes prepared from alcohol/acid-fixed meiotic samples in any other eukaryotic species. The condensation of the Os48 sequences is dynamic during prophase I of meiosis. The FISH signals derived from the Os48 repeat progress from a condensed configuration between leptonema and early pachynema into a decondensed structure from middle pachynema to diakinesis, and then return to a condensed form at metaphase I
Keyword	[ Hide all but 1 of 35 ] chromatin chromosomal location chromosome condensation cytosine dna dna sequence fish fluorescence fluorescence in situ hybridization heterochromatic regions heterochromatin hybridization in situ in situ hybridization loci meiosis metaphase metaphase-i oryza sativa pachytene pachytene chromosome prophase region repeat repeated dna repetitive dna rice sequence signal site situ hybridization structure tandem tandem repeat

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