三点自交法和两点最大似然法构建水稻F2群体分子标记连锁图谱的比较

根据连锁遗传的原理，列出了三点自交法和两点自交最大似然(ML)法估算显性标记遗传距离的具体步骤和算法，将水稻F2群体含香味基因Aro及其连锁的RFLP数据转变为显性标记数据后，用上述两种方法构建的连锁图谱与用MAPMAKER软件计算共显性数据得到的图谱排序相同、标记间距离相近．但是标记数据存在较大程度偏分离时，由三点自交法构建的图谱中标记间图距有增大趋势．作者为提高作图精确性，简化计算过程，讨论了三点自交法对估算重组值的影响及其在分子标记作图中的应用价值，并建议将共显性标记转变为显性标记时进行两次自交ML法估算。

The Estimation of Linkage Relationships of Dominate Molecular Markers in Rice F2 Population with Three-Point Selfcross and Two-Point Selfcross Maximum Likelihood Method

Based on the theories of linkage inheritance, we estimate the genetic distances between dominant markers and list detail algorithms steps of both three-point selfcross and two-point selfcross maximum likelihood (ML). As the RFLP codominated data in a F2 population with the aroma gene of rice are changed into the corresponding dominate marker data, the linkage maps established by above both methods are similar to that computed by software MAPMAKER/version 3.0 based on codominated data. Also the order and distance between the markers are approximated. But three-point selfcross method will lead to a tendency to increase the marker distance values, if present of a greater degree of distorted segregation between marker distances. Her we are try to discuss the influence on estimation of recombination values with the three-point selfcross method on segregation distortion and the usage to mapping of molecular makers. To improve the mapping accuracy and simplify the estimation process, we suggest first starts to transform the codominate data into the dominate data, followed by the estimation of recombination fractions using the two-point selfcross ML method for two times.