Noor M A, Cunningham A L, Larkin J C
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Genetics. 2001 Oct;159(2):581-8. doi: 10.1093/genetics/159.2.581.
We examine the effect of variation in gene density per centimorgan on quantitative trait locus (QTL) mapping studies using data from the Drosophila melanogaster genome project and documented regional rates of recombination. There is tremendous variation in gene density per centimorgan across this genome, and we observe that this variation can cause systematic biases in QTL mapping studies. Specifically, in our simulated mapping experiments of 50 equal-effect QTL distributed randomly across the physical genome, very strong QTL are consistently detected near the centromeres of the two major autosomes, and few or no QTL are often detected on the X chromosome. This pattern persisted with varying heritability, marker density, QTL effect sizes, and transgressive segregation. Our results are consistent with empirical data collected from QTL mapping studies of this species and its close relatives, and they explain the "small X-effect" that has been documented in genetic studies of sexual isolation in the D. melanogaster group. Because of the biases resulting from recombination rate variation, results of QTL mapping studies should be taken as hypotheses to be tested by additional genetic methods, particularly in species for which detailed genetic and physical genome maps are not available.
我们利用黑腹果蝇基因组计划的数据和已记录的区域重组率，研究了每厘摩基因密度变化对数量性状基因座（QTL）定位研究的影响。在整个基因组中，每厘摩的基因密度存在巨大差异，并且我们观察到这种差异会在QTL定位研究中导致系统性偏差。具体而言，在我们对随机分布于物理基因组中的50个等效效应QTL进行的模拟定位实验中，始终能在两条主要常染色体的着丝粒附近检测到非常强的QTL，而在X染色体上则常常检测到很少或没有QTL。这种模式在不同的遗传力、标记密度、QTL效应大小和超亲分离情况下都持续存在。我们的结果与从该物种及其近缘物种的QTL定位研究中收集的经验数据一致，并且解释了在黑腹果蝇组的性隔离遗传研究中所记录的“小X效应”。由于重组率变化导致的偏差，QTL定位研究的结果应被视为有待通过其他遗传方法进行检验的假设，特别是在没有详细遗传和物理基因组图谱的物种中。
