RESEARCH OF SEX-DEPENDENT MEIOTIC RECOMBINATION FREQUENCY IN MOUSE GENOME

在15号染色体远端的[(B6^&lt；Ca&gt；xMSm)x MSm]N_2(n=595)和[B6x(B6^&lt；Ca&gt；xMSm)]N_2(n=325)两个亚种间回交组合上进行微卫星标记，发现雄性的S重组率是雌性的10倍。这表明该染色体区域存在性别相关的重组热点或冷点。为了研究这一区域是热是冷，我们通过与BAC克隆的物理定位，估计了微卫星标记D15Mit40和D15Mit15在该区域的物理距离。由此产生的物理距离约为1兆碱基对。根据先前的报道，这些标记之间的遗传距离雌性为0.17 cM，雄性为5.23 cM。将小鼠基因组上每一物理距离的平均重组频率与观察到的遗传距离进行比较，表明雌性在该区域存在冷点，雄性在该区域存在热点。几个小鼠品系的杂交表明，重组频率的性别差异取决于所使用的品系。关于雌性和雄性的重组频率的全基因组研究目前正在进行中。初步结果表明，在小鼠基因组中存在几个重组的高频点。

We found that the male' s recombination frequency was as ten times much as the female' s one on the distal part of chromosome 15 by PCR-SSCP method with microsatellite markers on two intersubspecific backcross panels, [(B6^<Ca>xMSM)x MSM]N_2 (n=595) and [B6x(B6^<Ca>xMSM)]N_2 (n=325). This shows that a sex-dependent recombination hot or cold spot exists on this chromosome region. To investigate whether this spot is hot or cold, we estimated the physical distance between microsatellite markers, D15Mit40 and D15Mit15, on this region by physical mapping with BAC clones. The resultant physical distance was about one mega-base pair. As previously reported the genetic distance was 0.17cM in female and 5. 23cM in male between these markers. A comparison of an average recombination frequency per physical distance on mouse genome with the observed genetic distances indicated that a cold spot exists in female, a hot one in male on this region. Several crosses of mouse strains suggested that this sex-dependent difference of recombination frequency depended on strains used. Genome wide research is now in progress on recombination frequencies of females and males. Preliminary results suggest that several high frequency spots of recombinations exist in the mouse genome.