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How did evolution optimize circadian clocks?

Posted September 16, 2014
circadian clock
(a-c) Results from a previous experiment on the circadian clocks of hamsters shows that long and short pulses affect the circadian clock at different times of day. (d) In humans, the observed phase-response curve does not have a dead zone, but the intrinsic phase-response curve does have a dead zone, a feature of optimal circadian clocks. The new model can explain these observations. Credit: Hasegawa and Arita. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License.


From cyanobacteria to humans, many terrestrial species have acquired circadian rhythms that adapt to sunlight in order to increase survival rates. Studies have shown that the circadian clocks in some organisms have certain characteristics, such as multiple light input pathways, different gene expression patterns by different light pulses, and the presence of “dead zones” when the clock seems to become insensitive to light stimuli.


Now in a new study published in Physical Review Letters, Yoshihiko Hasegawa at The University of Tokyo and Masanori Arita at the National Institute of Genetics in Shizuoka and the RIKEN Center for Sustainable Resource Science in Kanagawa, all in Japan, have discovered new insight into these characteristics.

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