ANALYSIS OF SATELLITE DNA SEQUENCE OF SUNCUSU MURINUS.

我们从BamHI消化的鼠尾鱼基因组DNA中克隆了6个卫星DNA片段(PSB)。这些克隆都被定位到与异色C-带区位置一致的亚着丝粒区域。序列分析表明，(TTC)重复序列约3000个拷贝聚集在卫星DNA中。以寡核苷酸(TTC)6为探针的FISH分析表明，(TTC)6只优先与两个姐妹染色单体中的一个杂交。姐妹染色单体上的这种不对称杂交在过去使用的任何探针中都没有报道。为了阐明(TTC)n重复不对称杂交的生物学意义，我们提出了姐妹染色单体打印假说，该假说认为姐妹染色单体可能被不同的遗传机制修饰以区分染色单体。这种机制可以控制姐妹染色单体的选择性分离，导致一组确定的姐妹染色单体分配给子细胞。

We have cloned six satellite DNA fragments (pSBs) from the BamHI digested genomic DNA of Suncus murinus. These clones were all mapped to the subcentromeric regions coinsistent with the locations of heterochromatic C-banded regions. Sequence analysis of these clones showed that approximately 3000 copies of the (TTC) repeat were clustered in the satellite DNA.FISH analysis using oligonucleotide (TTC)6 as a probe revealed that (TTC)6 was preferentially hybridized to only one of the two sister chromatids. Such asymmetric hybridization on the sister chromatids has not yet been reported in any probes used in the past. To elucidate the biological significance of the asymmetric hybridization of the (TTC)n repeat, we proposed the "Sister chromatid printing hypothesis" which suggest that each of the sister chromatids might be differentially modified to distinguish chromatids by the unknown genetic mechanisms. This machinary may control the selective segregation of the sister chromatids, resulting in the allocation of a definite set of sister chromatids to the daughter cells.