Mulley J, Turner G, Bain S, Sutherland G R
Department of Histopathology, Adelaide Children's Hospital, Australia.
Am J Med Genet. 1988 May-Jun;30(1-2):567-80. doi: 10.1002/ajmg.1320300158.
Linkage data using the markers F9, DXS105 (cX55.7), DXS98 (4D-8) and DXS52 (St14) are presented from 22 kindreds segregating with the fragile X. Two-point linkage analysis was carried out taking into account cytogenetic results and penetrance classes defined by mental impairment status of mothers. Recombination frequencies (theta) corresponding to the maximum z scores (z) were obtained between F9 (z = 3.48, theta = 0.18), DXS105 (z = 5.06, theta = 0.07), DXS98 (z = 4.79, theta = 0.01) and DXS52 (z = 6.44, theta = 0.09) and the fragile X. Recombination frequencies between marker loci in fragile X families are also presented. These recombination frequencies need to be combined with those from other studies in order to determine the best estimates of map distances for use in genetic counselling, until markers closer to the fragile X, or at the fragile X, can be used. Most potential fra(X) heterozygotes were informative for flanking markers using the above 4 probes. Carrier risks were determined by 3-point analysis using informative flanking markers, taking into account cytogenetic results. Low level fra(X) expression occurred in 2 probable non-carriers; emphasising the need for extreme caution in the interpretation of low rates of expression.
本文呈现了来自22个与脆性X相关系谱的连锁数据，这些系谱使用了F9、DXS105（cX55.7）、DXS98（4D - 8）和DXS52（St14）标记。考虑到细胞遗传学结果以及根据母亲智力障碍状况定义的外显率类别，进行了两点连锁分析。在F9（z = 3.48，θ = 0.18）、DXS105（z = 5.06，θ = 0.07）、DXS98（z = 4.79，θ = 0.01）和DXS52（z = 6.44，θ = 0.09）与脆性X之间获得了对应最大z分数（z）的重组频率（θ）。还呈现了脆性X家族中标记位点之间的重组频率。在能够使用更接近脆性X或位于脆性X处的标记之前，这些重组频率需要与其他研究的结果相结合，以便确定用于遗传咨询的最佳图谱距离估计值。使用上述4种探针，大多数潜在的脆性X杂合子对侧翼标记具有信息性。考虑到细胞遗传学结果，通过使用具有信息性的侧翼标记进行三点分析来确定携带者风险。在2名可能的非携带者中出现了低水平的脆性X表达；这强调了在解释低表达率时需要极度谨慎。
