the other traits we analysed, because a large proportion of variance is explained by a common SNP in a single gene (ABO). We show that the variance attributed to a single major gene can be captured by all the SNPs on that chromosome or the whole genome, demonstrating that our whole-genome and chromosome estimation approach is independent of the distribution of effect sizes. Our results provide further evidence for the highly polygenic nature of complex trait variation and that a substantial proportion of genetic variation is tagged by common SNPs4,29. These results have implications for the experimental design to detect additional variation and are informative with respect to the nature of complex trait variation.
