Studies on circadian rhythms in Drosophila melanogaster beyondperiod mutants

Circadian rhythms are ubiquitous in biology, yet little is known about how they are generated or reset to environmental cues. A behavioral genetic strategy was applied to study circadian rhythms in the fruit fly, Drosophila melanogaster. Two screens for rhythm mutants were performed. One was a screen of known eye and brain mutants. This identified disconnected (disco) as an arrhythmic mutation. Later, the proportion of disco flies that are arrhythmic was found to be lower than for the other arrhythmic mutation; ;The Clock mutation was characterized extensively. The locomotor activity, eclosion, and song behavior of Clk mutants was studied. After this semi-dominant mutation proved of unmappable by cytogenetics, Clk was found to map close to per by recombination experiments. Molecular transformation experiments showed that this mutation is almost certainly an allele of per.;Photo-entrainment experiments were done to learn about the circadian photoreceptors and to describe the kinetics of locomotor activity phase shifting. It was found that flies are able to shift locomotor activity phase rapidly by as much as 5 hours. Rhythmic (and disco) flies showed a slight phase lag; ;Dietary deprivation and metabolic mutant experiments on the role of rhodopsin in photo-entrainment were not conclusive, but they suggested differences in the photosensitivity of locomotor activity and eclosion. Preliminary experiments in which photoreceptor specific gene-expressing cells were ablated did not seem to abolish flies' ability to entrain. Attempts to prove whether the eyes and ocelli can contribute to entrainment were also not conclusive.;Further studies on entrainment, and on Clk, disco, and other new rhythm mutants will lead to more information about the physical location, entrainment, organization, and function of the pacemaker in Drosophila. Based on the results described here, several hypotheses and the means to test them are proposed.