In this study we estimate that ~45%, ~17%, ~25% and ~21% of phenotypic variation for height, BMI, vWF and QTi, respectively, is tagged by common SNPs and we partition this variation onto autosomes, chromosome segments and the X-chromosome. We find that chromosome segments explain variation in approximate proportion to the total length of genes contained therein. While this suggests that there are very many polymorphisms affecting these traits, the linear relationship between the estimate of variance explained and genomic length is not perfect, especially for BMI and vWF. Chromosomes with similar (genic) lengths can explain different amounts of variation (Fig. 1 and Supplementary Fig. 4) and the estimates of variance explained by genomic segments with equal length also show large variability (Supplementary Fig. 5), suggesting some granularity in distribution of causal variants. The genetic architecture of vWF is distinct from 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
