Fig. 1. The electron transport chain decreases expression with age in humans, mice, flies and worms. Rows represent either human tissues or model organisms. Columns correspond to 95 genes in the electron transport chain gene set. Scale represents the normalized slope of the change in log₂ expression level with age. Grey indicates that genes were not present in that species. Original data from Zahn et al. (Zahn et al., 2006).