It is expected that many genes of very small effect size contribute to the genetic variance of complex behavioural phenotypes like personality. We estimated the empirical power our sample provides to detect genetic variants explaining 1% and 0.5% of the phenotypic variance by running association tests on simulated datasets in Merlin. The simulated datasets that are generated are similar to the original data in terms of marker informativeness, allele frequency, trait distribution, and missing data patterns, but original phenotypic values and individual’s genotypes for a selected SNP are replaced. The selected SNP is simulated such that it accounts for a specified proportion of the variance. The Merlin command we used is ‘--simulate --trait [variable name],[SNPname],0.01,0.39,0.60’, implying that the marker accounts for 0.01 of the phenotypic variance for a trait with a heritability of 0.40. The selected SNP we choose had a minor allele frequency of 0.25. For more information about the simulation procedure see http://www.sph.umich.edu/csg/abecasis/Merlin/reference/simulation.html.
