Nat. Genet. 38, 626–635 (2006); published online 28 April 2006; corrected online 5 May 2006; corrected after print 29 August 2007

In the version of this article initially published, two of the smaller bar plots in Figure 1e were mistakenly duplicated. Specifically, the Zfp385 plot is an erroneous copy of the 137774 plot, and the Txndc7 plot is an erroneous copy of the Pik3r5 plot. See below for the corrected version of the figure. This error does not change the conclusions of the study in any way, as the bar plots are just a few visual examples of more than 5,000 tag clusters, and the correct plots follow the same distribution patterns as the erroneous ones. This error has been corrected in the HTML and PDF versions of the article.