摘要目的确定一个染色体隐蔽结构异常的核型，探讨染色体表面看来为末端缺失的形成机理。方法　显微切割制备7号和7q亚端粒(7q36→qter)探针，通过荧光原位杂交（FISH）技术分析一例具有反复流产史且常规G带发现有7q末端缺失的病例。结果　发现该病例为母源的染色体1p32和7q32→q35区域之间的隐蔽插入易位，7q36→qter区域没有插入到1号染色体中，异常的7号染色体不是一个末端缺失而是一个中间缺失。结论　本研究为染色体末端区域的插入易位仍然保留其端粒区域提供了实验证据，符合三断裂重排的概念。中间缺失可能是解释细胞遗传学上见到的末端缺失的又一个机制。FISH与显微切割技术相结合，是检出染色体微小结构异常的一个强有力的工具。

abstractsObjective To determine the karyotype of a cryptic structural abnormality and explore the mechanism of apparent chromosomal terminal deletion. Methods Fluorescence in situ hybridization(FISH) with a whole chromosome 7 painting probe and a 7q subterminal probe (7q36→qter), prepared by chromosome microdissection technique, was used to analyze a case with a history of spontaneous abortion and 7q terminal deletion detected by conventional G-banding technique. Results The case was a maternal cryptic insertional translocation between chromosome region 1p32 and 7q32→q35. The region of chromosome 7q36→qter was not inserted into chromosome 1, and the abnormal chromosome 7 was not a terminal deletion but an interstitial deletion. Conclusions Chromosome insertion of the terminal region retains its telomere, which is consistent with the concept of a three-break rearrangement. Interstitial deletion may be regarded as another mechanism for terminal deletion in the chromosome banding level. Combined with chromosome microdissection, FISH technique could be a powerful diagnostic tool for detecting chromosome structural abnormalities.