Distribution of distance between head to head gene pairs in eight eukaryotic organisms. The distances between TSSs of head to head gene pairs were calculated in eight organisms individually. The distance distribution curves were then smoothed using Kernel Density Estimation. The binomial distribution can be observed in all the eight charts, where the minor peak represents the enrichment of bidirectional promoters.
Xu et al. BMC Systems Biology 2012 6(Suppl 1):S21 doi:10.1186/1752-0509-6-S1-S21