phenotypic consequences. For example, the load of a motif instance for which no variation is observed equals zero, while the load of a motif instance with a common mutation mapping to it that results in a severe loss of PWM match score is close to 0.5 (see Figure 3a for real-life examples). As would be expected for a metric quantifying deleterious effects, motif load showed a monotonic decreasing distribution in both flies and humans (Figure S3 in Additional file 1).
