Nagamine Yoshitaka, Pong-Wong Ricardo, Visscher Peter M, Haley Chris S
National Institute of Livestock and Grassland Science, Tsukuba 305-0901, Japan.
Genet Sel Evol. 2009 Oct 6;41(1):44. doi: 10.1186/1297-9686-41-44.
Simultaneous detection of multiple QTLs (quantitative trait loci) may allow more accurate estimation of genetic effects. We have analyzed outbred commercial pig populations with different single and multiple models to clarify their genetic properties and in addition, we have investigated pleiotropy among growth and obesity traits based on allelic correlation within a gamete.
Three closed populations, (A) 427 individuals from a Yorkshire and Large White synthetic breed, (B) 547 Large White individuals and (C) 531 Large White individuals, were analyzed using a variance component method with one-QTL and two-QTL models. Six markers on chromosome 4 and five to seven markers on chromosome 7 were used.
Population A displayed a high test statistic for the fat trait when applying the two-QTL model with two positions on two chromosomes. The estimated heritabilities for polygenic effects and for the first and second QTL were 19%, 17% and 21%, respectively. The high correlation of the estimated allelic effect on the same gamete and QTL test statistics suggested that the two separate QTL which were detected on different chromosomes both have pleiotropic effects on the two fat traits. Analysis of population B using the one-QTL model for three fat traits found a similar peak position on chromosome 7. Allelic effects of three fat traits from the same gamete were highly correlated suggesting the presence of a pleiotropic QTL. In population C, three growth traits also displayed similar peak positions on chromosome 7 and allelic effects from the same gamete were correlated.
Detection of the second QTL in a model reduced the polygenic heritability and should improve accuracy of estimated heritabilities for both QTLs.
同时检测多个数量性状基因座（QTL）可能会使遗传效应的估计更加准确。我们使用不同的单模型和多模型分析了远交商业猪群体，以阐明它们的遗传特性，此外，我们还基于配子内的等位基因相关性研究了生长和肥胖性状之间的多效性。
使用单QTL和双QTL模型的方差分量法，对三个封闭群体进行了分析，群体（A）是来自约克夏和大白合成品种的427头个体，群体（B）是547头大白个体，群体（C）是531头大白个体。使用了4号染色体上的6个标记和7号染色体上的5至7个标记。
在应用两个染色体上两个位置的双QTL模型时，群体A的脂肪性状显示出较高的检验统计量。多基因效应以及第一个和第二个QTL的估计遗传力分别为19%、17%和21%。同一配子上估计的等位基因效应与QTL检验统计量之间的高度相关性表明，在不同染色体上检测到的两个独立QTL对两个脂肪性状都有多效性影响。使用单QTL模型对群体B的三个脂肪性状进行分析，在7号染色体上发现了类似的峰值位置。来自同一配子的三个脂肪性状的等位基因效应高度相关，表明存在一个多效性QTL。在群体C中，三个生长性状在7号染色体上也显示出类似的峰值位置，并且来自同一配子的等位基因效应是相关的。
在模型中检测到第二个QTL降低了多基因遗传力，并且应该提高两个QTL估计遗传力的准确性。
