Cover image

Cover A “genetic circuit” represents the complex heritability at a single disease locus. For the past century, it has been widely acknowledged that independently segregating loci contribute to the overall risk of complex diseases, but the possible presence of multiple causative alleles at a single disease locus has been largely unexplored. In this issue, a single GWAS locus for hypertension is shown to harbor multiple alleles that contribute to overall disease risk and susceptibility to end-organ damage. (Cover illustration by Erin Fassbender, erin fassbender design, efassbender@sbcglobal.net. [For details, see Flister et al., pp. 1996–2002.])