Figure 2. Temporal profiles of clock gene transcripts in retina explants cultured for 72 h. Each graph shows data from four independent experiments (n = 3 per time point in each experiment). The mRNA amounts (log units) are expressed relative to the mean value found at a time point common to the four experiments: 28 h of culture. Mean values±standard error of the mean (SEM) are shown together with the best fitted sine wave curve. Alternating rectangles at the top indicate the projection of the lighting schedule (black: 12 h dark; hatched: 12 h light) to which the animals were exposed before they were euthanized.