CHROMOSOME 5-SPECIFIC REPETITIVE DNA-SEQUENCE IN RICE (ORYZA-SATIVA L.)

Repetitive DNA sequences in the rice genome comprise more than half of the nuclear DNA. The isolation and characterization of these repetiti ve DNA sequences should lead to a better understanding of rice chromos ome structure and genome organization. We report here the characteriza tion and chromosome localization of a chromosome 5-specific repetitive DNA sequence. This repetitive DNA sequence was estimated to have at l east 900 copies. DNA sequence analysis of three genomic clones which c ontain the repeat unit indicated that the DNA sequences have two sub-r epeat units of 37 bp and 19 bp, connected by 30-to 90-bp short sequenc es with high similarity. RFLP mapping and physical mapping by fluoresc ence in situ hybridization (FISH) indicated that almost all copies of the repetitive DNA sequence are located in the centromeric heterochrom atic region of the long arm of chromosome 5. The strategy for cloning such repetitive DNA sequences and their uses in rice genome research a re discussed.