Moreover, when we assumed SNPs contributed equally to risk for OCD, regardless of MAF, we obtained good fit between estimated OCD heritabilities from MAF bins of our sample and what was expected based on the distribution of MAF in 1000 Genomes data (Figure 1). SNPs affecting risk appear to be distributed at random over chromosomes because size was a good predictor of a chromosome’s contribution to total heritability (Figure 2). Chromosome 13 showed the poorest fit to this model, which may be partially explained by it having one of the lowest gene densities (6.5 genes per Mb) among human chromosomes. All of these results fit expectations of the infinitesimal quantitative genetics model.
