Nature Reviews Genetics 13, 36–46 (2012)

In the above article, Table 1 provided a URL for software called 'SNiPer'. This should have been a URL for software called 'Sniper'. The correct URL (http://kim.bio.upenn.edu/software/sniper.shtml) has been inserted, and in Table 1 and in the two occurrences in the main text, the word 'SNiPer' has been changed to 'Sniper'.

Also, references to Figure 3b and Figure 3c have been reversed.

The article has been corrected online. The authors and editors apologize for these errors.