RESEARCH OF SEX-DEPENDENT MEIOTIC RECOMBINATION FREQUENCY IN MOUSE GENOME

利用微卫星标记对两个亚种间回交板[（B6^<Ca>xMSM）x MSM]N_2（n=595）和[B6 x（B6 ^xMSM<Ca>）] N_2（n=325）进行PCR-SSCP分析，发现在15号染色体远侧部分，雄性的重组频率是雌性的10倍。这表明在该染色体区域存在性别依赖的重组热点或冷点。为了研究这一点是热还是冷，我们估计的物理距离微卫星标记，D15 Mit 40和D15 Mit 15，在这一地区的物理定位与BAC克隆。由此产生的物理距离大约是一个兆碱基对。遗传距离在雌性中为0.17cM，在雌性中为5。在这些标记之间的男性中为23 cM。将小鼠基因组上每个物理距离的平均重组频率与观察到的遗传距离进行比较，发现在该区域雌性存在一个冷点，雄性存在一个热点。小鼠品系的几个杂交表明，这种性别依赖的重组频率差异取决于所使用的品系。全基因组研究正在进行中的重组频率的女性和男性。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.