Biology 1002B Lecture Notes - Chronobiology, The Transcript, Cyanobacteria

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Published on 15 Apr 2013
School
Western University
Department
Biology
Course
Biology 1002B
Professor
Lecture 24: Biological Timekeeping
Circadian clock
Diurnal Phenomena
o Reoccurs daily
Foraging/predatory behaviour
Sleep-wake cycles
Body temperature
Hormone secretion
Photosynthesis
o It acts like a sine function, goes up and down
The value of keeping track of time
o What if organisms could anticipate environmental change?
Know when sun goes up and down
Think of advantage
Conserve energy
o Lhcb2 mRNA
Photosynthetic gene, light antenna around PSII
There’s no transcript during the night, only appears during the day
Measure transcript abundance, using northern blot
Transcription vs. mRNA decay
This is not a response to light, because it begins to synthesis when it is still dark
It anticipate that light is going to come on
The transcript abundance start when it is still dark
o It is continued under constant light
The cycle continues with constant light
o How can you explain this?
Not just response to light
Endogenous biological clock
Circadian rhythm
Question: what is the advantage of anticipation (check online)
Circadian rhythms
o Circadian rhythm biological rhythm with a period of “around” a day (24 hours)
sometimes more sometimes less
o Based on internal clock
o Two major criteria
Can be set by the external time (environment)
Can be set of what is going on outside, can be based on the sun
Free-running
Not slaved to the external time
So when environment is constant, the cycle continues, it runs by itself
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Document Summary

It acts like a sine function, goes up and down. Know when sun goes up and down. There"s no transcript during the night, only appears during the day. This is not a response to light, because it begins to synthesis when it is still dark. It anticipate that light is going to come on. The transcript abundance start when it is still dark. Question: what is the advantage of anticipation (check online) Circadian rhythms: circadian rhythm biological rhythm with a period of around a day (24 hours) sometimes more sometimes less, based on internal clock, two major criteria. Can be set by the external time (environment) Can be set of what is going on outside, can be based on the sun. So when environment is constant, the cycle continues, it runs by itself. Eventually, the free-running clock can get out of whack, must be trained again. E. g. body temperature and hormone under circadian control, even under constant environment.

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