with stronger-scoring minor alleles have a zero load irrespective of frequency. Using the human data presented an additional challenge of interpreting heterozygous genotypes. Since the immediate phenotypic trait associated with TFBS's match to consensus (that is, TF binding) occurs in cis, we have taken the decision to consider each human allele separately. We did not focus exclusively on homozygous genotypes, as this approach would further reduce the statistical power of the analysis that was already limited by the low variation rates in the human genome.
