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

为了研究与重复序列有关的基因组结构，我们从黑腹果蝇基因组文库中提取随机克隆，将其定位在唾液腺染色体上。从噬菌体文库中随机选取800个克隆，用原位杂交法确定231个克隆的染色体位置。142个克隆被定位在唯一位点上，89个克隆被定位在多染色体位点上。从这些克隆的分布中可以区分出两组克隆，这些克隆的序列在染色体上有多个拷贝。一组由拷贝数相对较少的克隆（2-6）组成，而另一组在染色体上有超过10个拷贝。将这些克隆与拟蝇（drosophila simulans）的染色体进行比对，发现前者克隆在相同的位置或具有相同的拷贝数。另一方面，后者通常具有较小的拷贝数，并且被映射到不同的位置。这些结果表明，前者主要由多基因家族组成，后者含有转座子。我们现在正在分析这些克隆体的详细分子结构。

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.