"rare variant",这是进行全基因组关联作图(genome-wide association,GWA),时可能会遇到的问题.所谓的稀有,其实就是其字面意思,等位基因频率较低,低到什么程度才算稀有,这个具体的研究有关(which, although we have adopted
the convention <1% frequency, might range from <0.1% to <0.01%, depending on the context,Bansal et al,2010,Nature reviews  Genetics,Statistical analysis strategies for association studies involving rare variants,http://blog.sciencenet.cn/home.php?mod=space&uid=479743&do=blog&id=459453).不过植物的关联作图这个可能不是什么问题,因为植物中,可以很方便地利用连锁作图方法.关联作图群体中的稀有等位基因,在特定组合的分离群体中就不再是什么稀有等位基因了.从作图而言,在植物中,当然比人类好操作多了.

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Rare Variant Association Analysis Methods for Complex Traits Annual Review of Genetics