Note: This content is accessible to all versions of every browser. However, this browser does not seem to support current Web standards, preventing the display of our site's design details.


Biological Clocks - Explaining Aschoff's Rule for a Transcription-Translation Model.

Have you ever thought about why you get tired or why you get hungry? Something in your body keeps track of time. It is almost like you have a clock that tells you when to do all those things. And indeed, in the suparachiasmatic region of our hypathamolous reside cells which each act like an oscillator, and together form a coherent circadian rhythm to help our body keep track of time. In fact, such circadian clocks are not limited to mammals but can be found in many organisms including single–cell, reptiles and birds. The study of such rhythms constitutes a field of biology and forms the background of my talk. Pioneers of this field, Pittendright and Aschoff, studied biological clocks from an input-output view, across a range of organisms by observing and analyzing their overt activity in response to stimulus such as light. Their study was made without recourse to knowledge of the biological underpinnings of the circadian pacemaker. The advent of the new biology has now made it possible to “break open the box” and identify biological feedback systems comprised of gene transcription and protein translation as the core mechanism of a biological clock. My research focuses on a simple transcription-translation clock model which nevertheless possesses many of the features of a circadian pacemaker including it entrainability by light. This model consists of two nonlinear coupled and delayed differential equations. Light pulses can reset the phase of this clock, whereas constant light of different intensity can speed it up or slow it down. This latter property is a signature property of circadian clocks and is referred to in chronobiology as “Aschoff’s rule”. In this talk we will explore why this simple clock follows Aschoff’s rule.

Type of Seminar:
Public Seminar
Henrik Ohlsson
Mar 14, 2005   14:00

ETH Zentrum, Physikstrasse 3, Zurich, Building ETL, Room K 25
Contact Person:

Prof. M. Morari
File Download:

Request a copy of this publication.
Biographical Sketch: