Transcription factors are proteins that bind and recognize specific sites of the DNA and regulate gene expression. Ct (cut) is a gene that encodes a transcription factor requires for development of Johnston’s organ, the auditory organ in the Drosophila antenna. Our laboratory uses Drosophila melanogaster, an easily manipulated experimental animal to test the target genes regulated by ct in the Johnston’s organ. Based on microarray data, we hypothesize that ct regulates the expression Cyp4 and Cyp6 genes. Cyp4 genes are up regulated and Cyp6 genes are down regulated in the ct mutant during the development if the auditory system in Drosophila melanogaster. We will also test whether knockout Cyp4 AND Cyp6 genes by recombination will phenocopy the ct mutant defects in the antenna. Mammalian ct homologs are expressed in the developing inner ear, but their function is unknown. Therefore, this study will provide a model for understanding the development of the human auditory system.