Figure 1. Effect of genotype on circadian period and its variability in male hamsters.

Mean (±SEM) τ_DD (top) and phase variation (bottom) of the time of activity onset (black bars), offset (hatched bars) or acrophase (white bars) of the first-order regression line used to determine τ_DD in male hamsters bearing wild type, tau, and duper alleles in various combinations. Posthoc analysis indicated statistically significant differences in τ_DD of activity onsets at the P<0.05 level: TTDd = TTDD>TTdd>TtDD>ttDD>Ttdd>ttdd (Tukey HSD test; TtDd did not differ from TTdd and TtDD). Statistical differences between genotypes in τ_DD of activity offset and acrophase showed similar patterns. Note that while strains differ markedly in τ_DD, phase variation is generally similar between genotypes. For phase rariation of activity onset and offset, only ttdd and TTdd groups differed from each other at the P<0.05 level; for phase variation of acrophase, ttdd>TTDD = TTdd. In all genotypes, phase variation of τ_DD based on activity offset is greater than phase variation of τ_DD assessed for onsets or acrophase.