Goonewardena P, Gustavson K H, Holmgren G, Tolun A, Chotai J, Johnsen E, Pettersson U
Clin Genet. 1986 Oct;30(4):249-54. doi: 10.1111/j.1399-0004.1986.tb00604.x.
Fragile-X mental retardation (FRAX-MR) is one of the more common X-linked disorders affecting 1 in 1,500 newborn males. This disease is characterized by the expression of fragile site in the region q27.3 of the X-chromosome of affected boys when their lymphocytes are cultured in folate deficient medium. In most patients there is macroorchidism postpubertally. The clinical diagnosis of carrier females based on the expression of fragile site in Xq27.3 is usually difficult and sometimes impossible. About half of the carrier females escape diagnosis by this method. Furthermore, prenatal diagnosis is not always feasible. Using Restriction Fragment Length Polymorphism (RFLP) and cloned DNA segments from the region Xq27-Xqter as probes, we have investigated Swedish families with FRAX-MR in three generations. Interesting observations, previously unreported to our knowledge, have been made in some patients and carrier mothers, using one of the probes which is localized to the distal end of Xq. The significance of these findings and the linkage of the disease locus to the different probes used in this study is presented.
脆性X智力低下（FRAX-MR）是较常见的X连锁疾病之一，每1500名新生男婴中就有1人受其影响。这种疾病的特征是，当受影响男孩的淋巴细胞在叶酸缺乏的培养基中培养时，其X染色体的q27.3区域会出现脆性位点。大多数患者在青春期后会出现巨睾症。基于Xq27.3中脆性位点的表达对女性携带者进行临床诊断通常很困难，有时甚至无法诊断。大约一半的女性携带者通过这种方法无法被诊断出来。此外，产前诊断也并非总是可行。我们使用限制性片段长度多态性（RFLP）以及来自Xq27-Xqter区域的克隆DNA片段作为探针，对三代患有FRAX-MR的瑞典家庭进行了研究。使用位于Xq远端的其中一种探针，我们在一些患者和携带者母亲身上有了有趣的发现，据我们所知，这些发现此前尚未有报道。本文将阐述这些发现的意义以及该疾病位点与本研究中所使用的不同探针之间的连锁关系。
