Figure 3.

Potential transcriptional triggers of mutational action by stage in Drosophila melanogaster. Changes in transcription may signal that the organism is employing its genome in developmentally novel ways, testing systems not previously used by the organism and potentially triggering mortality. Two measures of the rate of such change are plotted. The blue line is a mean of how severely individual genes are being up- or downregulated between adjacent stages. The red line indicates how many genes are being expressed at higher levels than they have at any previous stage. Time scale is linear within, but not between, life stages and the y-axis is scaled to the maximum value of each function. The peaks in transcriptional change early in the pupal phase suggest that risk is associated with many transitions, but both functions are highest in the earliest stages of embryonic development.