Barbi G, Steinbach P, Baur S, Vogel W
Hum Genet. 1985;69(2):106-8. doi: 10.1007/BF00293277.
Fibroblasts from a heterozygous carrier for the Martin-Bell syndrome, who manifests the fragile site Xq27, were cloned to separate the population carrying the primary defect on the active X chromosome from the population with this defect on the inactive X. Clones with this defect on the active X manifest the fra(X)(q27) whereas clones from the other population are fra(X)-negative (Steinbach et al. 1983b). In this project, the replication status of the X chromosome manifesting the fra(X)(q27) was studied in seven clones with this defect on the active X. The results obtained on the clones were very similar to the results obtained from uncloned fibroblasts and lymphocytes. In the clones the fragile site was found manifested on the early replicating X in 73 cells and on the late replicating X in four cells. Since the defect is located on the active X chromosome of these cells the manifestation of the fragile site on the late replicating X suggests that the defect and the fragile site cannot be identical. It is concluded that there is no obligate synteny of this defect and the manifested fragile site.
对一名马丁 - 贝尔综合征杂合携带者的成纤维细胞进行克隆，该携带者表现出脆性位点Xq27。目的是将活跃X染色体上携带主要缺陷的细胞群体与失活X染色体上有此缺陷的细胞群体分离。活跃X染色体上有此缺陷的克隆表现出fra(X)(q27)，而来自另一群体的克隆则为fra(X)阴性（施泰因巴赫等人，1983b）。在本项目中，对活跃X染色体上有此缺陷的7个克隆中表现出fra(X)(q27)的X染色体复制状态进行了研究。在克隆上获得的结果与从未克隆的成纤维细胞和淋巴细胞获得的结果非常相似。在这些克隆中，发现73个细胞的脆性位点表现在早期复制的X染色体上，4个细胞的脆性位点表现在晚期复制的X染色体上。由于缺陷位于这些细胞的活跃X染色体上，脆性位点在晚期复制的X染色体上的表现表明缺陷和脆性位点并非完全相同。得出的结论是，该缺陷与表现出的脆性位点不存在必然的同线性。
