Drosophila sex determination.
Transcription regulation is the process of the regulation of gene activity by regulating the process of the DNA to RNA conversion. It is achieved by firstly limiting the amount of mRNA produced by the DNA and then secondly by the post-transcriptional modification of that mRNA. Thus the process of transcriptional regulation is achieved by the cell.
The somatic sex determination in Drosophila is dependent on the expression of sex-lethal Sxl gene. The level of Sxl gene is determined by the number of X chromosomes and sets of autosomes ratio i.e. X:A ratio. The molecular mechanism of the Sxl gene transcription is positively or negatively controls the somatic sex determination.
The transcription regulation of Sxl gene is done by regulating the transcriptional promoter and several genes that encode the transcriptional factors of the helix-loop-helix family like the sis-b, da, dpn and emc.
The male or female offspring is determined by the Sxl (switch gene) in response to X:A ratio. When the Sxl gene is turned on in females by a positive X:A autoregulatory feedback loop the Sxl protein ensures the splicing of the female-specific Sxl transcripts. And the failure in the initiation of Sxl gene in early transcription leads to the development of the male offspring.
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