Cracking the Clock: Ronald J. Konopka and Seymour Benzer
Matthew Hardcastle; PNAS September 28, 2021 118 (39) e2115546118.
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Figure: Seymour Benzer with a model of a fruit fly. Reprinted with permission from ref. 3, which is licensed under CC BY 4.0.
For most life on Earth, the rising and setting of the sun coincides with daily patterns of activity. However, biological organisms have internal clocks that orchestrate their daily rhythms even in the absence of sunlight. These circadian rhythms, which set the schedule for the sleep–wake cycle, are the reason people feel jetlag when crossing time zones. On a cellular level, circadian rhythms control patterns in metabolism and other biological processes that fluctuate throughout the course of a day.
The existence of daily rhythms has been observed since antiquity, but early evidence that these patterns are set by an internal mechanism, rather than by sunlight alone, came from French scientist Jean-Jacques d’Ortous de Mairan in 1729. After observing that mimosa plants open their leaves during the day and close them at night, d’Ortous de Mairan wondered how the plants would behave in total darkness. He found that mimosa plants kept in total darkness continued to open and close their leaves on more or less the same schedule.
Before long, other researchers observed internal daily cycles in plants and animals, including humans, but the biological processes underpinning circadian rhythms would remain a mystery for the next two centuries. Current understanding of circadian rhythms, as well the field of circadian biology, owes its start to a now classic 1971 PNAS article, “Clock mutants of Drosophila melanogaster,” by Ronald J. Konopka and Seymour Benzer
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