disequilibrium between marker and trait variant, would require approximately 27000 unrelated individuals, with more realistic effect sizes of 0.001 or 0.00075 requiring samples of 45,000 or 61,000. Imperfect linkage disequilibrium (D’=.9) with a modest mismatch between genetic marker allele frequency and trait allele frequency (0.15 versus 0.05) would increase required sample sizes approximately 4-fold (e.g. 188,000 for a variant accounting for 0.001% of the variance).
