What is a clock made of?  We think of springs, gears and moving parts made out of metal.  But a clock could, in theory, be designed with almost any material.  There are water clocks, sundials, and electromagnetic oscillators that all function to tell time.  What difference does it make if the parts are made of liquids, laser beams, or plastic?  What if a clock was made of biological material—would it be any less a device for keeping time?  Would it surprise you that such clocks exist in your body and in every living thing?

In living things, biological clocks are given the name circadian systems.  They help organisms from bacteria to humans adjust to day-night (diurnal) cycles or other natural rhythms like seasons.  They control metabolic levels, feeding, reproduction and most other biological functions.  As scientists peer into the mechanisms behind circadian systems, they are finding remarkable similarities to man-made clocks.  One PhysOrg article was entitled, “Finding mechanism behind bacteria’s biological clock” – i.e., “how these biological clocks work at the level of biochemical mechanism.” Scientists at the University of California at Merced uncovered one clever mechanism: “One of the proteins, in the course of a 24-hour cycle, shifts from being squishy to hard and then back to squishy. The changes lead to all three proteins connecting and disconnecting.”  So it’s not just the connections proteins make with each other because of their shapes, but also their flexibility.  The article ended by saying these discoveries are changing the way researchers look at biological clocks.  “It’s now believed the proteins are more involved than previous [sic] thought.”

PhysOrg also reported last month that scientists at Tel Aviv University are studying the biological clocks in zebrafish for clues to help humans.  A gene called Period2, “also present in humans,” responds to light and helps calibrate the clock.  It has a region called Light Responsive Model, they said.  “Within this region” (of the gene), they said, “there are short genetic sequences called Ebox, which mediate clock activity, and Dbox, which confer light-driven expression.”  The interplay between these sequences is responsible for synchronization of the circadian system.  Remarkably, “In these fish cells, the human LRM behaved in exactly the same way, activating Period2 when exposed to light — and unveiling a fascinating connection between humans and the two-inch-long fish,” even though, according to evolution, fish and mammals have been separated by many millions of years….

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