Mutations and molecules influencing biological rhythms.

Rhythmically oscillating phenomena in biological systems have been analyzed in many ways: behaviorally (reviews: Moore-Ede et al 1982, Saunders 1982), neurobiologically (reviews: Turek 1985, Jacklet 1985), and biochemically (reviews: Takahashi & Menaker 1984, Johnson & Hastings 1986). Over the last four years, another angle from which these rhythms has been approached-"clock genetics"-appears to have also come to the fore. Yet, this area of rhythm studies has been around for at least 20 years (previous summaries: Feldman et a1 1979, Konopka 1981). In the present review we update several of the recent genetic advances and also discuss how such investigations are moving into the molecular area in studies of two organisms, Drosophila and Neurospora. The biological clocks underlying rhythmic fluctuations have seemed to be an eternal mystery. Whether "clock molecular genetics" will allow us soon to peer into the core mechanisms of the pertinent oscillators remains to be seen. Interpretation of the studies of these clocks is not always simple. That is, a fair amount of jargon surrounds rhythm analysis. Consequently we begin by listing some of the properties of true clocks, which are deeper than simply that they control various "parameters" that exhibit some kind of regular fluctuations having a given periodicity, such as a "circadian tau," or cycle durations in the ultradian realm (ca. 10-1 to 10-3 of a day; reviews: Shultz & Lavie 1985). We note these additional attributes of