Embryonic utilization measured by Affymetrix tiling arrays. (a) Consistent trend of utilization across EST and tiling experiments. Median differences in tiling array fluorescence intensities were used to detect transcription at 4,664 peaked and broad promoters. The total number of transcribed sites was plotted for each of the 12 time points, corresponding to 2-hour increments during embryogenesis. The promoters were separated into two groups at each time point: those with embryo EST associations and those without. (b) Developmental condition is correlated with initiation patterns. The set of all promoters was divided into 3,788 peaked and 876 broad. At every time point, the fractions of transcribed peaked and broad promoters were found by dividing the number of transcribed promoters in each group by the total number of peaked and broad promoters, respectively.