GWAS on the Island of Kosrae Figure 4. Study power over varying effect sizes. A known effect explaining 0.5%, 1% or 2% of phenotypic variance was ‘‘spiked’’ into a dataset of 770 randomly selected SNPs with MAF$0.01. Study power was evaluated using a combined score from within- and between-family tests of association (QFAM-Total) with genomic control. A) Of 770 spiked datasets generated, power is measured as fraction of datasets in which the ‘‘spiked’’ SNP exceeds a particular p-value threshold. These data were used to estimate an effective sample size for Kosrae, from which power estimates for effects explaining up to 8% of phenotypic variance were generated (panel B). doi:10.1371/journal.pgen.1000365.g004 seven SNPs tag a causal allele common to both populations or whether independent causal variants segregate in these two ethnic groups. Besides SNPs near APOC3/A5 and triglycerides, no other loci across all 15 traits achieved genome-wide significance (Table 3). The most compelling evidence for a novel finding is observed in the association results for thyroid stimulating hormone (TSH). Among the top 20 results for TSH, 10 SNPs (p = 9.961027 to 4.861026) map to chromosome 9 at 97.6–97.8 Mb, a region encompassing the gene thyroid transcription factor 2 (TTF-2) PLoS Genetics | www.plosgenetics.org 7 February 2009 | Volume 5 | Issue 2 | e1000365