Date of Award

Spring 1998

Document Type

Restricted Thesis

Terms of Use

© 1998 Lynn T. Matthews. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology Department

First Advisor

Kathleen King Siwicki

Abstract

Circadian rhythms of eclosion and locomotor activity in Drosophila require the clock genes period and timeless. The RNA and protein products of these genes cycle in a circadian fashion. Their underlying role in clock function is demonstrated by mutations to them which affect overt rhythms. Our experiments explore the cellular link between this molecular clock and the overt behavioral rhythm of eclosion. Dissected Drosophila neural tissues (brain, ventral ganglion and ring gland, or CNS-RG) were maintained in culture and monitored in constant dark for expression of the clock gene, period. Animals were transgenic for a period-luciferase (per-luc) gene such that per transcription could be reported by photons produced by the luciferase reaction. Isolated CNS-RG complexes exhibited a circadian rhythm of per-driven luc expression which dampened and became arrhythmic after several days in culture. Exposing tissues to 24 hour light-dark or 25°C:18°C temperature cycles delayed dampening and coordinated the phases of the rhythms, showing that the per-luc rhythms are entrainable and that both temperature and light function as zeitgebers to the system. These results demonstrate that isolated CNS-RG complexes include pathways for interpreting clock-setting stimuli and machinery for entraining the molecular circadian clock. Experiments which monitored per-driven luc output from isolated CNS and RG tissues demonstrated that CNS preparations possess an endogenous clock. The data from the RG preparations, however, suggest that the culturing system may be insufficient to detect their output. These data offer insight into the origin of per-luc rhythms monitored in the CNS-RG complex. Further, the observed damping of rhythms and the evidence for an endogenous light and temperature sensitive clock in the CNS offer support to the multiple oscillator model for cellular control of circadian output (Pittendrigh et al. 1958).

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