Final answer:
In eukaryotic cells, regulatory proteins are expressed in response to signals and molecules that regulate gene expression. Transcription factors bind to specific regulatory DNA sequences to control gene expression by either turning genes on or off.
Step-by-step explanation:
In eukaryotic cells, the expression of regulatory proteins is controlled by a complex process involving various signals and molecules. Cells respond to extracellular environmental signaling, such as chemicals or hormones, which bind to specific receptors on the cell surface or intracellularly. These signals ultimately lead to the production of transcription factors, which bind to specific regulatory DNA sequences associated with the genes they control. The binding of transcription factors to these regulatory sequences can either turn on or off the expression of genes, depending on the specific sequence and context.