Hultén M A, Tease C, Lawrie N M
LSF Research Unit, West Midlands Regional Genetic Services, Birmingham Heartlands Hospital, Birmingham B9 5PX, UK.
Chromosoma. 1995 Nov;104(3):223-7. doi: 10.1007/BF00352187.
The X chromosome pair was identified in diakinesis/metaphase I stage mouse oocytes using a repeat sequence DNA probe and fluorescence in situ hybridisation. Chiasma positions along the X bivalent were measured in 57 oocytes from 4 females. Overall, our observations showed that while there were no obvious "hotspots" for chiasma formation along the X chromosome, there was a tendency to favour the distal end. Minimum inter-chiasma distances were substantial indicating the occurrence of strong genetic interference. Estimates of both genetic distances and recombination fractions for any interval along the chromosome can be calculated from the chiasma data. The average chiasma frequency for the X bivalent was 1.37 giving an estimated total genetic map length of 68.5 cM. In general, the pattern of chiasma distribution along the X chromosome resembled that anticipated from recombination distances in published consensus linkage maps. There were, however, some intriguing differences between the two approaches. The reason for these discrepancies are unknown but may be related to lack of precision in cytogenetic mapping of loci, inter-strain and/or interspecies differences in the genetic controls over the distribution of crossover events. One advantage of the chiasma analysis approach is its suitability for investigating these problems.
利用重复序列DNA探针和荧光原位杂交技术，在双线期/中期I阶段的小鼠卵母细胞中鉴定出了X染色体对。在来自4只雌性小鼠的57个卵母细胞中测量了沿X二价体的交叉位置。总体而言，我们的观察结果表明，虽然沿X染色体没有明显的交叉形成“热点”，但有偏向远端的趋势。交叉间的最小距离很大，表明存在强烈的遗传干扰。可以从交叉数据计算出沿染色体任何区间的遗传距离和重组率的估计值。X二价体的平均交叉频率为1.37，估计的总遗传图长度为68.5 cM。一般来说，沿X染色体的交叉分布模式与已发表的共识连锁图中重组距离所预期的模式相似。然而，这两种方法之间存在一些有趣的差异。这些差异的原因尚不清楚，但可能与基因座细胞遗传学定位的精度不足、交叉事件分布的遗传控制中的品系间和/或种间差异有关。交叉分析方法的一个优点是它适合研究这些问题。
