The Drosophila Biological Clock
This animation explores the molecular interactions that regulate circadian rhythms in Drosophila fruit flies.
Most organisms have circadian rhythms, biological processes that operate on 24-hour cycles. These rhythms are regulated by an internal timekeeping mechanism called the biological clock. The animation explores a series of cyclically expressed proteins that maintain the biological clock in Drosophila.
The animation begins by introducing the gene period (per), which encodes a protein, PER, that accumulates and degrades in regular cycles. The per gene is activated by the transcription factors CYC and CLOCK. As PER builds up during the night, it represses the CYC-CLOCK complex, creating a negative feedback loop. After daybreak, PER is degraded and CYC-CLOCK is reactivated, starting the cycle again.
The next section of the animation introduces the timeless (tim) gene, which encodes a protein, TIM, that binds to and stabilizes PER. The animation also discusses the roles of Doubletime, a protein that accelerates the degradation of PER, and Cryptochrome, a light-activated protein that destroys TIM. The animation ends by demonstrating how a mutation in Doubletime affects the rest of the biological clock pathway.
This animation is a clip from a 2000 Holiday Lecture Series, Clockwork Genes: Discoveries in Biological Time. Depending on students’ background, it may be helpful to pause the animation at various points to discuss different proteins or parts of the pathway.
circadian rhythm, feedback loop, fruit fly, phosphorylation, transcription factor