FAIRE/Pol II occupancy signals for introns and exons by position. (a, b) Box plots showing signal distributions for Pol II occupancy (a) and FAIRE (b) in spliced genes by exon or intron number (E1 for exon1, I1 for intron1, and so on). The average signal for each intron position was compared to the average signal for each previous exon in order to assess statistical significance. Box widths are proportional to the number of probes in each class and position tested. Signals in exon/intron sets (marked with lines and symbols) are significantly different (*P < 2.2 × 10-16, §P < 7.2 × 10-7, †P < 5.6 × 10-13, ‡P < 0.0007, +P < 6.7 × 10-09; Welch two sample t-test).
Wilhelm et al. Genome Biology 2011 12:R82 doi:10.1186/gb-2011-12-8-r82