Composite profiles over 5527 genes for histone occupancy (with anti-histone H3 or H4) and mock control (with no antibody) in yeast , (a) before and (b) after normalization. The boundaries of ORFs were defined by transcription start and stop sites and were scaled to [0, 1]. The upstream and downstream regions are plotted with the same scale with the ORF. Before normalization, the mock control appears to show the same differential enrichment between genic and intergenic regions as the histone occupancy, suggesting that the differential enrichment may be an artifact. However, after normalization, the mock control no longer shows significant differential enrichment while H3 and H4 profiles still do.