Mulligan L M, Phillips M A, Forster-Gibson C J, Beckett J, Partington M W, Simpson N E, Holden J J, White B N
Am J Hum Genet. 1985 May;37(3):463-72.
We have tested linkage between the locus for the fragile-X [fra(X)] syndrome at Xq27.3 and five polymorphic restriction sites identified by four DNA probes mapping distal to Xq26.1. A maximum distance of approximately 15 centimorgans (cM) between Xq27.3 and the marker loci mapping to this region was predicted based on the physical chromosome length. Close linkage between the disease and marker loci was excluded for probes DXS19 and DXS37 (theta = .05, Z = -2.94 and Z = -4.17, respectively). These marker loci were estimated to be less than five cM apart but approximately 40 cM proximal to the fragile site, indicating that there is a significantly greater frequency of recombination in this region of the X chromosome than expected from the physical length. Linkage results for the other marker loci and the fra(X) syndrome were inconclusive. However, the pX45d probe locus appears very closely linked to the factor IX locus (Z = 1.94 at theta = 0) and is approximately 20 cM proximal to Xq27.3. A relative map of the polymorphic restriction sites, fra(X) syndrome locus, and factor IX locus was constructed by maximizing lod scores over the Xq26.1----q27.3 region.
我们检测了位于Xq27.3的脆性X [fra(X)] 综合征位点与由定位在Xq26.1远端的4个DNA探针所识别的5个多态性限制性位点之间的连锁关系。根据物理染色体长度预测，Xq27.3与定位到该区域的标记位点之间的最大距离约为15厘摩（cM）。对于探针DXS19和DXS37，排除了疾病与标记位点之间的紧密连锁（分别为θ = 0.05，Z = -2.94和Z = -4.17）。这些标记位点估计相距不到5 cM，但距离脆性位点约40 cM近端，表明X染色体的该区域重组频率明显高于根据物理长度预期的频率。其他标记位点与fra(X) 综合征的连锁结果尚无定论。然而，pX45d探针位点似乎与因子IX位点紧密连锁（θ = 0时Z = 1.94），并且距离Xq27.3约20 cM近端。通过在Xq26.1----q27.3区域最大化对数优势分数，构建了多态性限制性位点、fra(X) 综合征位点和因子IX位点的相对图谱。
