Response: Why It Is Time to Sequence

in 7313 children from a UK birth cohort, eliminating concerns of population stratification (St Pourcain et al., 2010). Like McClellan and King, we expect that with the development of highthroughput sequencing technologies, whole-genome sequencing will be an invaluable tool for the study of rare genetic variants contributing to complex diseases. However, the apparent importance of rare variants does not discount the contribution of common variants; the concerns about population stratification should not be overstated and certainly should not be presented as an argument to discredit many published GWAS signals with an odds ratio of less than 2. These sections within an otherwise excellent Essay must be countered so that Cell readers have a more balanced view of the current state of the field. Kai Wang,1 Maja Bucan,2 Struan F.A. Grant,1,3 Gerard Schellenberg,4 and Hakon Hakonarson1,3,* 1Center for Applied Genomics, Children’s Hospital of Philadelphia 2Department of Genetics 3Department of Pediatrics 4Department of Pathology and Laboratory Medicine University of Pennsylvania, Philadelphia, PA 19104, USA *Correspondence: [email protected] DOI 10.1016/j.cell.2010.07.025