Abstract
The
per gene of D. melanogaster influences or participates in the generation of biological rhythms. Previous experiments have identified the head as the location from which
per exerts its effect on circadian rhythms. To localize further this region and to examine the effects of altered levels and altered spatial expression patterns of the
per gene on circadian rhythms of locomotor activity, we have characterized transformed lines containing
per gene constructs missing substantial
cis-acting regulatory information. The data suggest that wild-type levels of
per gene expression are necessary in only a small fraction of the nervous system for near wild-type periods, whereas a larger fraction of
per-expressing cells in the brain contributes to the strength of the circadian rhythms.