The molecular organisation of a B chromosome tandem repeat sequence from Brachycome dichromosomatica.
A high copy, tandemly repeated, sequence (Bd49) specific to the B chromosome and located near the centromere in Brachycome dichromosomatica was used to identify lambda genomic clones from DNA of a 3B plant. Only one clone of those analysed was composed entirely of a tandem array of the B-specific repeat unit. In other clones, the Bd49 repeats were linked to, or interspersed with, sequences that are repetitious and distributed elsewhere on the A and B chromosomes. One such repetitious flanking sequence has similarity to retrotransposon sequences and a second is similar to chloroplast DNA sequences. Of the four separate junctions analysed of Bd49-like sequence with flanking sequence, three were associated with the same A/T-rich region in Bd49 and the fourth was close to a 25 bp imperfect dyadic sequence. No novel B-specific sequences were detected within the genomic clones.
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Department of Genetics, The University of Adelaide, Adelaide, South Australia 5005, Australia. jtimmis@genetics.adelaide.edu.au
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D001483:Base Sequence; D015139:Blotting, Southern; D002875:Chromosomes; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000302:isolation & purification; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D008969:Molecular Sequence Data; D010944:Plants / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
D018744:DNA, Plant; D015252:Deoxyribonucleases, Type II Site-Specific; C032229:GANTC-specific type II deoxyribonucleases; C035594:TTTAAA -specific type II deoxyribonucleases