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A sequence specific to B chromosomes of Brachycome dichromosomatica
U P John1, C R Leach, J N Timmis
1Department of Genetics, University of Adelaide, Australia.
Genome
|October 1, 1991
Summary
Researchers identified unique DNA sequences on supernumerary B chromosomes in the Australian plant Brachycome dichromosomatica. These sequences, including a 176-bp tandem repeat, are specific to B chromosomes and show variation in conservation and methylation.
Area of Science:
- Plant genetics and genomics
- Chromosome biology
- Molecular evolution
Background:
- Supernumerary B chromosomes contribute to numerical chromosome variation in plants and animals.
- Brachycome dichromosomatica is an Australian native plant with a simple A chromosome set and variable B chromosomes.
Purpose of the Study:
- To characterize DNA sequences specific to the B chromosomes of Brachycome dichromosomatica.
- To investigate the evolutionary relationships of these B-chromosome-specific sequences within the Brachycome genus.
Main Methods:
- Enrichment of DNA sequences unique to B chromosomes.
- Cloning and hybridization of enriched DNA fragments.
- Sequence analysis of B-chromosome-specific DNA clones, including a 176-bp tandem repeat family.
- Comparative analysis with DNA from related Brachycome taxa.
Main Results:
- Identified and characterized a family of 176-bp tandem repeats specific to the B chromosomes of B. dichromosomatica.
- Sequence analysis revealed differential conservation and potential methylation at NdeII sites within the repeat.
- The identified repeat shows homology to DNA from Brachycome ciliaris var. languinosa but not other local related taxa.
Conclusions:
- The 176-bp tandem repeat is a B-chromosome-specific element in Brachycome dichromosomatica.
- Sequence variation and potential epigenetic modifications (methylation) may play roles in B chromosome evolution.
- The distribution of this repeat suggests a specific evolutionary history within the Brachycome genus.