AP Biology/Control of Gene Expression
Gene expression is regulated by the pathways of transcription, translation, and eventual modification of proteins that are formed.
Gene expression starts at the DNA level with the transcription of the DNA to form mRNA by creating the complement of the DNA using RNA polymerase. In order to initiate transcription, one needs transcription factors which are specific to regions of the DNA. Transcription factors can increase the binding of RNA polymerase. Transcription factors can be formed from the cell or can be made of complexes, such as a hormone and hormone receptor which will bind to a region in the DNA called the hormone response element. Once RNA polymerase binds, then the next level of regulation is translation.
In prokaryotes, translation can be affected by the feedback of transcription on translation such as in the trp operon.
In eukaryotes, translation is influenced by the post-transcriptional modifications and the presence of the necessary factors for translation.