Figure 2.

The molecular timetable method of Ueda et al. [4]. (a) The expression of genes that oscillate in a 24 hour fashion is characterized by their molecular peak time (MPT). Schematized genes with specific circadian patterns of expression are represented by different symbols. An overlay of all oscillating expression patterns should ideally render an even distribution of maximal gene expression over the 24 hour day. Note that the diagram is double plotted and displays two days (48 hours). This molecular timetable can be used to generate a diagram of MPT distribution at a single time point, such as ZT = 12 (boxed). (b) Representation of the MPT at a single time point with a fitted cosine curve at ZT = 12; genes with MPTs of 12 are maximally expressed. (c) A schematic diagram for detecting body time (BT). A standard cosine curve (solid line) for tissue harvested at ZT = 12 is shown. The maximal normalized expression level indicates standard BT (BT_S). The cosine curve of tissue collected at ZT = 12 of individual 1 (dotted line) reveals a BT₁ about 2 hours earlier than BT_S. Individual 2 displays a delayed cosine curve (hatched line, BT₂). (d) A plot of normalized gene expression of a clock-mutant individual. The scattered distribution does not allow fitting of a cosine curve.