人染色体脆性部位超微结构及其形成机制研究

①目的 探讨人染色体脆性部位（Fra)超微结构及其形成机制。②方法 用低叶酸、低小牛血清和较高pH值培养方法，常规外周血染色体制片，Giemsa染色，光镜下选择并确定有Fra的染色体做标记并照相，Carnoy固定液退油、褪色，临界点干燥，离子喷镀金膜，将做标记的同一Fra进行扫描电镜观察、照相，最后经图像处理仪（KY－EM－I型）分析处理。③结果 光镜下1例Fra 1q25和2例Fra 3p14均为染色单体断裂；电镜下Fra 1q25为狭窄裂隙，第1例Fra 3p14为狭窄裂隙，第2例Fra 3p14为缢痕形态。④结论 Fra的形成可能为染色质纤维包装不全所致，且这种包装不全存在着不均一性。

A STUDY ON THE ULTRASTRUCTURE OF HUMAN CHROMOSOMAL FRAGILE SITE AND ITS FORMATION MECHANISM

Objective To study the ultrastructure of human chromosomal fragile site and its formation mechanism. Methods \ Peripheral blood cell culture with low concentration of serum folate and higher pH in the medium was used. Routine peripheral blood preparation of chromosome was made and stained by Giemsa. Those chromosomes with fragile site location were selected and determined by LM(light microscope) and marked and photographed. Deoiled and destained with carnoy fixed. The slides were critical point dried. Having been dried, slides were mounted on metal stubs and coated with gold in ION coater (IECO.IB 3). The same fragile site marked was examined by JSM 840 SEM(scanning electron microscope) and photographed. Finally, processed by image analysis technique (Ky EM I type).\ Results\ One Fra 1q25 and two Fra 3p14 showed chromatid breaks by LM. Fra 1q25 was found to be a narrow gap. First Fra 3p14 showed a narrow gap . The second Fra 3p14 showed chromosome constriction shape in SEM.\ Conclusion\ The ultrastructure of fragile site showed its formation may be undercondensation of chromatin fibers. And this undercondensation can be non distributive.