Bickel S E, Wyman D W, Orr-Weaver T L
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
Genetics. 1997 Aug;146(4):1319-31. doi: 10.1093/genetics/146.4.1319.
The ord gene is required for proper segregation of all chromosomes in both male and female Drosophila meiosis. Here we describe the isolation of a null ord allele and examine the consequences of ablating ord function. Cytologically, meiotic sister-chromatid cohesion is severely disrupted in flies lacking ORD protein. Moreover, the frequency of missegregation in genetic tests is consistent with random segregation of chromosomes through both meiotic divisions, suggesting that sister cohesion may be completely abolished. However, only a slight decrease in viability is observed for ord null flies, indicating that ORD function is not essential for cohesion during somatic mitosis. In addition, we do not observe perturbation of germ-line mitotic divisions in flies lacking ORD activity. Our analysis of weaker ord alleles suggests that ORD is required for proper centromeric cohesion after arm cohesion is released at the metaphase I/anaphase I transition. Finally, although meiotic cohesion is abolished in the ord null fly, chromosome loss is not appreciable. Therefore, ORD activity appears to promote centromeric cohesion during meiosis II but is not essential for kinetochore function during anaphase.
ord基因对于果蝇雌雄减数分裂中所有染色体的正确分离都是必需的。在此，我们描述了一个ord无效等位基因的分离，并研究了缺失ord功能的后果。在细胞学上，缺乏ORD蛋白的果蝇减数分裂姐妹染色单体黏连严重受损。此外，遗传测试中的错分离频率与两个减数分裂过程中染色体的随机分离一致，这表明姐妹染色单体黏连可能完全被消除。然而，ord无效果蝇的活力仅略有下降，这表明ORD功能对于体细胞有丝分裂期间的黏连并非必不可少。此外，在缺乏ORD活性的果蝇中，我们未观察到生殖系有丝分裂的扰动。我们对较弱ord等位基因的分析表明，在中期I/后期I转换时臂黏连释放后，ORD对于正确的着丝粒黏连是必需的。最后，尽管ord无效果蝇的减数分裂黏连被消除，但染色体丢失并不明显。因此，ORD活性似乎在减数分裂II期间促进着丝粒黏连，但对于后期动粒功能并非必不可少。
