Institute of Animal Husbandry and Breeding, University of Hohenheim, D-70599 Stuttgart, Germany.
J Anim Breed Genet. 2010 Jun;127(3):171-9. doi: 10.1111/j.1439-0388.2009.00847.x.
The present study used published quantitative trait loci (QTL) mapping data from three F2 crosses in pigs for 34 meat quality and carcass traits to derive the distribution of additive QTL effects as well as dominance coefficients. Dominance coefficients were calculated as the observed QTL dominance deviation divided by the absolute value of the observed QTL additive effect. The error variance of this ratio was approximated using the delta method. Mixtures of normal distributions (mixtures of normals) were fitted to the dominance coefficient using a modified EM-algorithm that considered the heterogeneous error variances of the data points. The results suggested clearly to fit one component which means that the dominance coefficients are normally distributed with an estimated mean (standard deviation) of 0.193 (0.312). For the additive effects mixtures of normals and a truncated exponential distribution were fitted. Two components were fitted by the mixtures of normals. The mixtures of normals did not predict enough QTL with small effects compared to the exponential distribution and to literature reports. The estimated rate parameter of the exponential distribution was 5.81 resulting in a mean effect of 0.172.
本研究利用猪的三个 F2 杂交群体的已发表数量性状位点(QTL)定位数据，对 34 个肉质和胴体性状进行了分析，得出了加性 QTL 效应和显性系数的分布情况。显性系数是通过观察到的 QTL 显性偏离除以观察到的 QTL 加性效应的绝对值来计算的。该比值的误差方差使用 delta 方法进行近似。使用一种改进的 EM 算法，通过混合正态分布（混合正态分布）来拟合显性系数，该算法考虑了数据点的异质误差方差。结果表明，拟合一个分量更为合适，这意味着显性系数呈正态分布，估计均值（标准差）为 0.193（0.312）。对于加性效应，混合正态分布和截断指数分布都进行了拟合。混合正态分布拟合了两个分量。与指数分布和文献报道相比，混合正态分布并不能很好地预测具有较小效应的 QTL。指数分布的估计率参数为 5.81，导致平均效应为 0.172。
