Genetic dissection of the circadian clock: A timeless story

The period (per) gene is known to play a critical role in the generation and/or maintenance of circadian rhythms in Drosophila. Efforts to identify other molecular components of pacemaking pathways recently led to the isolation of a new clock mutation, timeless (tim). Circadian rhythms are eliminated in tim flies, probably due to the effect tim has on the subcellular localization of period protein (PER). Data indicate that the putative product(s) of the tim locus is essential for timekeeping in Drosophila. In this article I will review the isolation and phenotype of the tim mutation and also discuss its interaction with per.