# The Drosophila circadian clock

> A clock-dial graphical abstract of the Drosophila molecular clock: the CLOCK–CYCLE activator switches on period and timeless at dawn, PER and TIM proteins build through the day and cross into the nucleus to shut their own genes off at night, and the ~24 h loop restarts. DOUBLETIME sets the delay; sunlight acting through CRYPTOCHROME removes TIM and resets the clock. The three founding period mutants (19 h, ~24 h, 28 h) are shown as small dials.

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- Open in the LabCanvas editor (LabCanvas account): https://www.labcanvas.com/editor.html?template=drosophila-circadian-clock
- Updated: 2026-10-14
- Category: Graphical abstracts
- Method: Graphical abstract
- Starting materials: The clock genes period and timeless and their activator CLOCK–CYCLE
- Product: A self-sustaining ~24 h oscillation of gene expression, reset each day by light
- Key result: Original period mutants: arrhythmic, 19 h and 28 h, from the normal ~24 h (Konopka & Benzer 1971); the work of Hall, Rosbash and Young won the 2017 Nobel Prize in Physiology or Medicine (Huang 2018)
- Figure: 1920 × 1080 px, 115 editable layers

## Steps

1. **Dawn · switch on**: CLOCK–CYCLE binds the E-box and drives transcription of period (per) and timeless (tim) (Darlington et al. 1998)
2. **Day · build up**: per and tim are transcribed and translated; DOUBLETIME phosphorylates PER to add delay, so per mRNA peaks in the early night and PER protein hours later (Huang 2018)
3. **Night · switch off**: PER and TIM pair and enter the nucleus, where they block CLOCK–CYCLE and shut off their own genes — closing the loop (Darlington et al. 1998)
4. **Light · reset**: Sunlight acting through CRYPTOCHROME removes TIM and resets the clock; light pulses advance or delay the rhythm (Myers et al. 1996; Emery et al. 1998; Ceriani et al. 1999)

## Uses

- Graphical abstracts on circadian rhythms and the molecular clock
- Teaching the transcription–translation feedback loop and light entrainment
- Talks on chronobiology and the 2017 Nobel Prize

## References

1. Konopka & Benzer, “Clock mutants of Drosophila melanogaster”, PNAS 1971. https://doi.org/10.1073/pnas.68.9.2112 (method origin)
2. Myers et al., “Light-induced degradation of TIMELESS and entrainment of the Drosophila circadian clock”, Science 1996. https://doi.org/10.1126/science.271.5256.1736 (primary)
3. Darlington et al., “Closing the circadian loop: CLOCK-induced transcription of its own inhibitors per and tim”, Science 1998. https://doi.org/10.1126/science.280.5369.1599 (primary)
4. Emery et al., “CRY, a Drosophila clock and light-regulated cryptochrome, is a major contributor to circadian rhythm resetting and photosensitivity”, Cell 1998. https://doi.org/10.1016/S0092-8674(00)81637-2 (primary)
5. Ceriani et al., “Light-dependent sequestration of TIMELESS by CRYPTOCHROME”, Science 1999. https://doi.org/10.1126/science.285.5427.553 (primary)
6. Huang, “The discoveries of molecular mechanisms for the circadian rhythm: the 2017 Nobel Prize in Physiology or Medicine”, Biomed. J. 2018. https://doi.org/10.1016/j.bj.2018.02.003 (review)

Credit: Drawn by LabCanvas after Konopka & Benzer, PNAS 1971 (doi:10.1073/pnas.68.9.2112); Myers et al., Science 1996; Darlington et al., Science 1998; Emery et al. and Stanewsky et al., Cell 1998; and Huang, Biomed. J. 2018 (doi:10.1016/j.bj.2018.02.003).

## Questions

**What does the “The Drosophila circadian clock” template show?** A clock-dial graphical abstract of the Drosophila molecular clock: the CLOCK–CYCLE activator switches on period and timeless at dawn, PER and TIM proteins build through the day and cross into the nucleus to shut their own genes off at night, and the ~24 h loop restarts. DOUBLETIME sets the delay; sunlight acting through CRYPTOCHROME removes TIM and resets the clock. The three founding period mutants (19 h, ~24 h, 28 h) are shown as small dials.

**What are the steps shown in “The Drosophila circadian clock”?** 1. Dawn · switch on: CLOCK–CYCLE binds the E-box and drives transcription of period (per) and timeless (tim) (Darlington et al. 1998). 2. Day · build up: per and tim are transcribed and translated; DOUBLETIME phosphorylates PER to add delay, so per mRNA peaks in the early night and PER protein hours later (Huang 2018). 3. Night · switch off: PER and TIM pair and enter the nucleus, where they block CLOCK–CYCLE and shut off their own genes — closing the loop (Darlington et al. 1998). 4. Light · reset: Sunlight acting through CRYPTOCHROME removes TIM and resets the clock; light pulses advance or delay the rhythm (Myers et al. 1996; Emery et al. 1998; Ceriani et al. 1999).

**What are the starting materials and the product?** Starting materials: The clock genes period and timeless and their activator CLOCK–CYCLE. Product: A self-sustaining ~24 h oscillation of gene expression, reset each day by light.

**Which papers is “The Drosophila circadian clock” based on?** Konopka & Benzer, “Clock mutants of Drosophila melanogaster”, PNAS 1971 (doi:10.1073/pnas.68.9.2112); Myers et al., “Light-induced degradation of TIMELESS and entrainment of the Drosophila circadian clock”, Science 1996 (doi:10.1126/science.271.5256.1736); Darlington et al., “Closing the circadian loop: CLOCK-induced transcription of its own inhibitors per and tim”, Science 1998 (doi:10.1126/science.280.5369.1599); Emery et al., “CRY, a Drosophila clock and light-regulated cryptochrome, is a major contributor to circadian rhythm resetting and photosensitivity”, Cell 1998 (doi:10.1016/S0092-8674(00)81637-2); Ceriani et al., “Light-dependent sequestration of TIMELESS by CRYPTOCHROME”, Science 1999 (doi:10.1126/science.285.5427.553); Huang, “The discoveries of molecular mechanisms for the circadian rhythm: the 2017 Nobel Prize in Physiology or Medicine”, Biomed. J. 2018 (doi:10.1016/j.bj.2018.02.003).

**Can I edit the “The Drosophila circadian clock” template?** Yes. Open it in the LabCanvas editor: all 115 layers are editable. Change the text, colours and layout, then export PNG, TIFF, SVG or PDF.

**Do I need an account to use this template?** Not to view it here. To open and edit it, sign in to LabCanvas or create a free account (the free plan keeps up to 3 designs). Downloading the figure is part of LabCanvas Pro (US$19 a month or US$199 a year).