A STUDY OF IDENTIFICATION AND QUANTIFICATION OF MIDDLE REPETITIVE SEQUENCES OF DROSOPHILA GENOME

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In order to study the genome structure concerning to the repetitive sequences we mapped random clones extracted from the genomic library of Drosophila melanogaster on the salivary gland chromosome. About 800 clones were randomly chosen from the phage library and chromosomal locations were determined for 231 clones by in situ hybridization. 142 clones were mapped on the unique locations and 89 clones were mapped on the multiple chromosomeal locations. Two groups of clones were distinguished from the distribution of these clones containing sequences which have multiple copies on the chromosome. One group is made of clones which has relatively small copy numbers (2-6) and the others have more than 10 copies on the chromosome. Mapping these clones to the chromosome of Drosopila simulans, the closely related species of D.melanogaster, it was found that the former group of clones were mapped on the same location and/or have the same copy numbers. On the other hand, the latter had generally smaller copy numbers and were mapped on different locations. These results suggest that the former clones are made of mainly multigene families and the latters contains transposons. We are now analyzing detailed molecular structure of these clones.