Normalized distribution of spanion clusters around distinct genetic landmarks. Human fragments are aligned at six key genetic landmarks and the preferred location of spanionclusters are presented on the plot. The individual distributions arranged into a single plot concatenating them in head to tail fashion representing a hypothetical gene. The original distributions are represented by alternating colours: IGR/5' UTR (blue); 5' UTR/intron (red); intron/exon (blue); exon/intron (red); intron/3' UTR (blue) and 3' UTR/IGR (red). In each case the point of the alignment is the junction of the two genetic features in question. The possible number of hits decreases with the distance from the selected landmark as fragments are considered only up to the next genetic borderline or 1 kb distance at most. Therefore the raw counts normalised with the maximal number of possible hits at each given position relative to the aligned landmark.