Germ - Line Transformation Involving D N A from the period Locus in Drosophila melanogaster : Over - lapping Genomic Fragments that Restore Circadian and Ultradian Rhythmicity to per ' and per - Mutants

P-element-mediated transformations involving DNA fragments from the period (per) clock gene of Drosophila melanogaster have shown that several subsegments of the locus restore rhythmicity to pero or permutants. Such fragments overlap in a genomic regjon complementary to one transcript, a 4.5-kb RNA which is probably the per message, in that it is necessary and (in terms of expression from this X-chromosomal locus) sufficient for the fly's circadian rhythms. It is also at least necessary for the high-frequency oscillations normally produced by courting males as they vibrate their wings. The entirety of the 4.5-kb transcript is not necessary for rather strong rhythmicity; nor does it seem to be sufficient, in transformants, for wild-type behavioral phenotypes. A 0.9-kb RNA, homologous to a genomic region immediately adjacent to the source of the 4.5-kb species, oscillates in its abundance over the course of a day; but coverage of this transcript source in several transformants carrying a pero mutation which eliminates the 0.9-kb RNA's oscillation does not restore rhythmicity. All of the independently isolated arrhythmic mutations tested were covered by the same array of overlapping per+ -derived DNA fragments, implying that the only portion of the locus which has mutated to arrhythmicity is complementary to the 4.5-kb transcript.