Mapping the clock rhythm mutation to the period locus of Drosophila melanogaster by germline transformation.

The Clock (Clk) mutation shortens circadian rhythms of locomotor activity and eclosion from ca. 24 h to 22.5-23 h. Clk was previously mapped, by meiotic recombination, very close to the period(per) locus on the X chromosome. To determine whether Clk is a mutation within the per gene or if the former is separate from the latter, two overlapping genomic fragments were cloned from Clk flies to produce a per-containing 13.2 kb construct, per01 flies (which by themselves are arrhythmic)--when transformed with this construct--expressed short-period rhythms. This indicates that the Clk mutation is contained within this 13.2 kb region and is almost certainly a new "fast-clock" allele of per.