侧翼标记基因型方差组分随不同选择强度的变化

从实际角度看，选择在用于标记-QTL连锁分析的实验群体中是较普遍存在的。为获得QTL位置及其效应的无偏估计，有必要研究选择对连锁分析实验所造成的影响。该文在侧翼标记情况下利用广泛使用的半同胞设计提出了3种方差组分，即标记组间方差、组内多基因方差和组内重组方差及其构成。着重从理论上研究了各方差组分在不同选择强度下的变化规律，阐明了选择对各方差组分的效应。结果表明，各方差组分对选择强度的变化很敏感。随着选择强度的增加，所有方差组分都以二次曲线方式有不同程度的下降。比较而言，标记组间方差组分下降最快，标记组内多基因方差下降较慢，组内重组方差下降最慢。这意味着QTL连锁分析功效的降低。所以在实际群体中应采取必要措施尽量避免选择的发生，从而消除选择对QTL连锁分析的负面效应。

Changes in Variance Components of Flanking Marker Genotypes Under Varying Selection Intensities

Selection is practically ubiquitous during marker-QTL linkage analysig with an experimental population. Thus, it is necessary to investigate the impacts of selection upon linkage analyses in order to obtain unbiased estimates of QTL position and effect. In this article, by exploiting flanking markers through the widely applied half-sib design, we have developed the structures of three variance components, i.e., variance component between marker genotypes, polygenic variance component and recombinant variance component within marker genotypes. Changes in these variance components under varying selection intensities were investigated in this study to formulate the effects of selection on various variance components. Results showed clearly that all variance components presented were quite sensitive to changes in selection intensity. As selection intensity increased, all variance compo- nents declined by differing extents in a quadratic fashion. Comparatively speaking, the variance between marker genotypes decreased most drastically, followed by the polygenic variance within marker genotypes and then the recombinant variance within marker genotypes, which suggested a decrease of power for QTL linkage analysis. Therefore, steps should be taken to avoid as much as possible the presence of selection in real populations, so as to further eliminate the negative effects of selection on QTL linkage analysis.