Disrupting Cryptochrome partly restores daily rhythms in fruit flies with a broken internal clock gene

A combination of a period-null mutation with cry(b) restores circadian rhythmicity in locomotor behavior in light-dark cycles.

• Null mutations in core genes like period and timeless lead to behavioral arrhythmicity in constant darkness.
• Light transduction pathways involving rhodopsins and cryptochrome are critical for the circadian clock's response to environmental light.
• The cry(b) mutation decreases light sensitivity but does not significantly disrupt locomotor activity rhythms due to rhodopsin compensation.
• Combining period-null and cry(b) mutations restores rhythmicity in light-dark cycles, indicating a potential role for timeless beyond its known functions.
• Circadian rhythmicity in constant darkness remains absent, with TIM protein not oscillating or localizing as expected in crucial brain neurons.

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