The circadian rhythm is mostly endogenous: it is ‘performed’ and regulated by chemical reactions that occur within the body’s cells, using internal cues. Though, it is also influenced by external stimuli like the amount of sunlight and other environmental factors.
In the 1970s, Seymour Benzer and Ronald Konopka found that in an as-yet unknown gene was responsible for regulating the body clock of fruit flies (Drosophila melanogaster). They called it the period gene. In 1984, Hall, Rosbash and Young, this year’s medicine laureates, found a protein called PER that was encoded by the period gene. They also observed that PER accumulated in cells at night and degraded during the day. Hall and Rosbash figured that PER blocked the activity of the period gene. In other words, it regulated its own production and degradation.
A third gene was discovered by the trio later, called doubletime, which encoded for a protein that was responsible for controlling the circadian rhythm’s periods.The Per-Tim-Dbt cycle provides only a simplistic picture of what happens.
The underlying phenomena continue to be studied widely to this day, especially to better understand their relationship with hormones and hormonal diseases, to explore how cells that don’t contain circadian regulations coordinate with cells that do, and to understand sleep disorders.