The Human Circadian Rhythm

Student writer: Trenton Beckendorff
Student editors: Belicia Tan
23andMe editor: Chelsea RobertsonThao Do

The Headline

  • Three scientists awarded the 2017 Nobel Prize in Physiology or Medicine for the discovery of genetic mechanisms that regulate the human circadian rhythm [1,2,3].

What is the human circadian rhythm?

Do you consider yourself a night owl, or an early bird? Humans, like all living organisms, have an innate biological clock, called the circadian rhythm, that affects “alertness, hunger, metabolism, fertility, mood and other physiological conditions” throughout the day [3]. Despite tremendous research efforts, the mechanisms underlying this biological cycling remained elusive, until recently.

How are genetics involved?

Using fruit flies, Drs Jeffrey C. Hall PhD, Michael Rosbash PhD, and Michael W. Young PhD identified a gene that regulates the cellular response to light throughout the day [3]. Because of its cyclic regulation patterns, the gene was appropriately named period [3]. The gene contains instructions for a protein, called PER, which builds up at night and slowly degrades during the day.

What is the impact of the discovery?

By identifying a mechanism that controls the circadian rhythm, this discovery enables scientists to gain a deeper understanding of how disruptions to the circadian rhythm may affect several aspects of human health, including “sleep disorders, obesity and mental health disorders” [3].

Thought Question for Students

Given this newfound discovery of the circadian rhythm, which area of future research do you find most interesting? Why?


  1. Chappell, B. (2017, October 02). Nobel Prize In Medicine Is Awarded To 3 Americans For Work On Circadian Rhythm. Retrieved January 09, 2018, from
  2. Kolata, G. (2017, October 02). 2017 Nobel Prize in Medicine Goes to 3 Americans for Body Clock Studies. Retrieved January 09, 2018, from
  3. NIH Grantees Win 2017 Nobel Prize in Physiology or Medicine. (2017, October 02). Retrieved January 9, 2018, from
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