The Clock Protein in Drosophila

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Another key study, performed by Darlington et al, analyzed the function of dCLOCK, the CLOCK protein in Drosophila. This study confirmed the identity of dclock, investigated the function of dCLOCK in regulation of the circadian genes per and tim, and demonstrated the function of PER and TIM in an inhibitory feedback loop (Darlington et al., 1998). First, a screen for a homolog of the mouse clock gene in Drosophila was conducted using the cDNA library of adult Drosophila heads and a probe of the mClock gene. A high yield of overlap in the clones confirmed the presence of a homolog of the mClock gene in Drosophila (Darlington et al., 1998). A Southern blot of Drosophila genomic DNA with a dclock probe produced only one band, indicating that dclock is in fact a single-copy gene (Darlington et al., 1998). Dclock was then used in a Northern blot to probe RNA from the entire body of Drosophila. Results showed that the probe hybridized to RNA in the head, the body, and the appendages of the fly (Darlington et al., 1998). This showed that the expression of dclock occurs at a variety of locations (Darlington et al., 1998). The expression of dclock was then analyzed in terms of the light-dark cycle. Expression patterns during the 24 hour time period confirmed that dclock oscillates with the circadian rhythm (Darlington et al., 1998). After the initial tests to establish dclock as a circadian gene were completed, the function of the protein dCLOCK in the regulation of transcription of
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