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 that the clock in your liver that regulates the feeding rhythm and the clock in your brain that regulates the sleep–wake rhythm are not in sync with each other.”
More questions were bound to come. “That is so cool! Is there a common mechanism by which these clocks operate?”
“Yes, there is. Every day, as if following the rising and setting of the sun, concentrations of different timekeeping protein complexes rise and fall inside almost every cell in our body. This happens just like a wave and repeats itself every 24 hours. By binding and releasing the DNA predictably, these protein complexes turn thousands of genes on and off. Most of our vital body functions, including blood pressure, body temperature, metabolism, and even our moods and habits fluctuate according to a precise 24-hour cycle,” I explained.
That’s so fascinating. Since you said that most cells have circadian clocks, I wonder whether there is an advantage
that cells or organisms get
by having a clock.”, her eyes
brightened at the thought.
“Yes, they do. From several experiments, we know that possessing a clock can give an intrinsic advantage, i.e., by optimally coordinating metabolic and physiological processes, for example, hunger and sleep should occur exclusive to each other. Another extrinsic advantage is that organisms with functional clocks can time their activities in an effective manner; for example, searching for food would be most effective when food availability is the highest. In fact, circadian clocks have been found to be present from bacteria to humans, and have
Mr. Chitrang Dani || 107
evolved independently multiple times. This substantiates the idea of clocks giving an advantage to organisms.” I was marveling at the elegance of this insight.
“I’m finding it unbelievable imagining that all those metabolic and physiological processes that I read about vaguely in my school biology textbook would be regulated in a rhythmic manner. But if so much is already known about circadian clocks and rhythms, what are you still doing research on?” she asked.
I took a deep breath to begin, “So most research on circadian rhythms has been carried out in controlled laboratory conditions in the presence of one time-cue. However, in natural environments, multiple time-cues are simultaneously present. Can you name some cues that can give information about time?”
After thinking for a second, she said,” Of course! Apart from light, there’s temperature, humidity, availability of food, predators, or let’s say managers/bosses at the office
for humans, etc.!”
Still laughing at her joke, I
added, “Yes, also these time- cues change throughout the day and also throughout the year. My objective is to see how circadian rhythms evolve in natural–like environments compared to laboratory ones. To do this, I am looking at rhythms of populations of Drosophila melanogaster, also called fruit flies, reared in standard lab conditions and comparing them with populations reared in an outdoor enclosure, under semi-natural conditions. Food is available to them at all times, and they are also protected from other predators, apart
   Her inquisitiveness encouraged me to explain further, “Well, your internal clock is actually
a system made up of multiple clocks. We have various clocks in the body– in the brain, liver, kidney, lungs, intestine, and all other organs that function pretty much like an orchestra. This is why when you feel sleepy and hungry at the same time, it suggests that the clock in your liver that regulates the feeding rhythm and the clock in your brain that regulates the sleep– wake rhythm are not in sync with each other.”
  
















































































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