(SE = 0.11, P = 1.2 × 10−7, likelihood-ratio test) of the phenotypic variance can be explained by all SNPs for gc and gf, respectively (Table 1). Analysing the English and Scottish samples separately or fitting 20 principal components as covariates in the model of analysis did not change the results markedly, nor did the inclusion of pairs of individuals whose estimated relatedness was > 0.025 (Supplementary Table 2). We subsequently partitioned additive genetic variation to individual chromosomes using the software package GCTA31, fitting all chromosomes simultaneously, and found that, on average, longer chromosomes explain more variation (Figure 2).
