These mice had a circadian period almost 2 hours shorter than wild-type animals.

In a study published in 2005, it was shown that plants whose circadian period matched the period of the light-dark cycle in its environment had increased photosynthesis and growth.

The average free-running circadian period for the strain of mice in Takahashi's lab is 23.7 hours.

For humans, the free-running circadian period is about 25 hours, which means that in a similar experiment the vertical bars on a human sleep-activity record would drift to the right.

If it had only one copy, it would show a lengthened circadian period of 24.8 hours, "clearly out of the distribution of normal mice," Takahashi said, but still perfectly regular.

Because the mutants displayed no circadian rhythms and the heterozygote flies displayed long circadian periods, they determined that cycle has a dominant phenotype.

Therefore, in rhythmic environments, the fitness of cyanobacteria is improved when the clock is operational and when its circadian period is similar to the period of the environmental cycle.

Unlike other chronotyping methods, which address the psychology of sleep, the MCTQ measures the phase angle of entrainment, the difference between an organism's intrinsic circadian period and the environmental light cycle.

Our concern about such errors motivated a comparison between three different numerical methods for estimating circadian period.

Recent research, however, has shown that CK1δ deficiency lengthens circadian period while CK1ε deficiency does not.