PHASE-SHIFTING OF THE CIRCADIAN CLOCK BY INDUCTION OF THE DROSOPHILA PERIOD PROTEIN

Virtually all organisms manifest circadian (24-hour) rhythms, governed by an ill-defined endogenous pacemaker or clock. Several lines of evi dence suggest that the Drosophila melanogaster period gene product PER is a clock component. If PER were central to the time-keeping mechani sm, a transient increase in its concentration would cause a stable shi ft in the phase of the clock. Therefore, transgenic flies bearing a he at-inducible copy of PER were subjected to temperature pulses. This tr eatment caused long-lasting phase shifts in the locomotor activity cir cadian rhythm, a result that supports the contention that PER is a bon a fide clock component.