Cloning and characterisation of polymorphic heterochromatic segments of Brachycome dichromosomatica |
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Authors: | Andreas Houben Gerhard Wanner Lynda Hanson Dawn Verlin Carolyn R Leach Jeremy N Timmis |
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Institution: | Department of Genetics, University of Adelaide, South Australia, Australia. andreas.houben@adelaide.edu.au |
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Abstract: | After selective enrichment and differential hybridisation of Cot-1 DNA fractions of plants with and without polymorphic heterochromatic segments, a repetitive sequence (called Bds1) specific
to the polymorphic chromosome segments of Brachycome dichromosomatica (Brachyscome dichromosomatica) was isolated. A single repeat unit of Bds1 is 92 bp long and is organised in tandem arrays at three different polymorphic
segment sites on the chromosomes of cytodeme A2. Although all three sites showed extensive polymorphism between plants, the
karyotypes of all analysed mitotic root cells were stable within a single plant. Electron microscopy revealed heavily condensed
chromatin structures at the most obvious polymorphic site. The mechanisms that generate and maintain the observed chromosome
structure polymorphisms are discussed.
Received: 16 March 1999; in revised form: 28 September 1999 / Accepted: 11 November 1999 |
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