A recessive mutant of Drosophila Clock reveals a role in circadian rhythm amplitude

Homozygous Clk(ar) Drosophila flies are viable but exhibit behavioral arrhythmicity.

• The Clk(ar) phenotype results from a mutation that disrupts gene splicing and reduces Clock activity.
• Molecular oscillations can still be detected in Clk(ar) flies despite their lack of rhythmic behavior.
• Analysis of transcription indicates that Clk(ar) significantly affects the levels and strength of transcriptional oscillations.
• Clk is suggested to play a major role in determining the strength and amplitude of circadian rhythms.

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