ISSN:
1573-6849
Keywords:
Nicotiana tabacum
;
nucleosome positioning
;
Progenitor-specific probes
;
repetitive DNA
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Members of a new family of highly repetitive DNA sequences called GRS were isolated fromNicotiana tabacum L. genomic DNA and characterized. Cloned, sequenced monomeric units (180–182 bp) of GRS exhibit properties characteristic of molecules that possess a stable curvature. The GRS family represents about 0.15% of total genomic DNA (104 copies per haploid genome) and could be derived from eitherNicotiana tomentosiformis orNicotiana otophora, two possible ancestors of the T genome of the amphidiploidN. tabacum. Sequence homology between the HRS60 (Koukalováet al. 1989) and the GRS family has been estimated to be 57%.In situ hybridization was used to localize GRS on mitotic chromosomes. Hybridization signals were obtained on five pairs of chromosomes at intercalary sites of the longer chromosome arms. The majority of GRS sequences appeared to be organized in tandem arrays and a minority were found to be dispersed through the genome in short clusters, interspersed with other types of DNA repeats, including 25S rDNA sequences. Several loci containing both GRS and HRS60 were also found. Such hybrid loci may indicate intergenomic transfer of the DNA in the amphidiploidN. tabacum. GRS sequences, like HRS60 (Fajkuset al. 1992), were found to specify the location of nucleosomes. The position of the nucleosome core has been mapped with respect to a conservedMbol site in the GRS sequence and an oligo A/T tract is a major centre of the DNA curvature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00713050
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