Dahl N, Malmgren H, Pettersson U, Holmgren G, Seemanová E, Gustavson K H
Department of Medical Genetics, Biomedical Center, Uppsala, Sweden.
Am J Med Genet. 1991 Feb-Mar;38(2-3):319-21. doi: 10.1002/ajmg.1320380230.
Diagnosis of the carrier status of the fragile X [fra(X)] syndrome was made in 2 unrelated women who did not express the fragile site. Both were related to several individuals with a typical fra(X) phenotype and the marker X chromosome. A restriction fragment length polymorphism (RFLP) approach was used with probes that flank the fra(X) locus (FRAXA). The loci used for risk calculations of the fra(X) genotype were DXS98 and DXS105 on the centromeric side and a recently characterized locus, DXS304, on the telomeric side. Coincidence correction for the distances between marker loci and FRAXA was made according to the Kosambi function. The DNA marker test gave the risk for one female to be a carrier of 99.7-99.9%. In another family a female was excluded from being a carrier with a probability of greater than 99.7%. The DNA marker U6.2, defining the locus DXS304, has increased the reliability of DNA based diagnosis of carrier status for females-at-risk. It is concluded that DNA analysis can serve as a valuable complement to chromosome analysis in families informative for the more closely linked flanking markers.
在2名未表现出脆性位点的不相关女性中诊断出脆性X [fra(X)]综合征的携带者状态。她们均与几名具有典型fra(X)表型和标记X染色体的个体相关。采用限制性片段长度多态性（RFLP）方法，使用位于fra(X)基因座（FRAXA）两侧的探针。用于计算fra(X)基因型风险的基因座在着丝粒侧为DXS98和DXS105，在端粒侧为最近鉴定的基因座DXS304。根据Kosambi函数对标记基因座与FRAXA之间的距离进行符合度校正。DNA标记检测得出一名女性为携带者的风险为99.7 - 99.9%。在另一个家族中，一名女性被排除为携带者，概率大于99.7%。定义基因座DXS304的DNA标记U6.2提高了对有风险女性携带者状态基于DNA诊断的可靠性。得出结论，在对更紧密连锁的侧翼标记有信息价值的家族中，DNA分析可作为染色体分析的有价值补充。
