1. Characterisation of repeated sequences from microdissected B chromosomes of Crepis capillaris
- Author
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Manuel Jamilena, Manuel A. Garrido-Ramos, M. Ruiz Rejón, J. S. Parker, and C. Ruiz Rejón
- Subjects
DNA, Plant ,Molecular Sequence Data ,Biology ,Polymerase Chain Reaction ,Chromosomes ,Micromanipulation ,Chromosome 16 ,Chromosome 18 ,Heterochromatin ,Sequence Homology, Nucleic Acid ,Chromosome 19 ,Genetics ,Constitutive heterochromatin ,Cloning, Molecular ,In Situ Hybridization, Fluorescence ,Genetics (clinical) ,Chromosome 12 ,DNA Primers ,Repetitive Sequences, Nucleic Acid ,B chromosome ,Base Sequence ,Plants ,Molecular biology ,Chromosome 17 (human) ,Blotting, Southern ,Chromosome 3 - Abstract
The B chromosome of Crepis capillaris was isolated from the standard chromosomes by microdissection, and the chromosomal DNA amplified using the degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR). The PCR product was cloned and a B-specific library created and characterised. Southern and in situ hybridisation analyses of the DOP-PCR product from microdissected B chromosomes confirmed that the B chromosome is composed mainly of sequences also present in the A chromosomes but lacks the main repeated DNA families located in the A-chromosomal heterochromatin. From 100 clones analysed, 12% of the generated B-chromosomal library was shown to be composed of dispersed repeats located in both the A and B chromosomes. No B-specific repeated sequence was detected. One of the most abundant repeated DNAs within the library, the family B134, was further characterised. Repeating units show a sequence similarity range from 69% to 90% and are characterised by their richness in (CA)n repeats. In situ hybridisation revealed that members of this family are dispersed throughout the A and B chromosomes but are more concentrated in the pericentromeric heterochromatin of the B, indicating that the molecular organization of B heterochromatin is different from that of the A chromosomes. Compared with the A chromosomes, the Bs contain about 20,000 copies per micron more of the B134 sequence. This indicates that B134 was amplified on the B chromosome after its origin. The B134 sequences in the B chromosomes have also diverged from those on the A chromosomes. Although the DNA composition of A and B chromosomes is similar, Bs are evolving separately from A chromosomes at the molecular level.
- Published
- 1995