Final answer:
Transcription factors are proteins that control gene expression by regulating the binding of RNA polymerase to specific genes, thus determining whether these genes are activated or repressed.
Step-by-step explanation:
Transcription factors are vital proteins that play a key role in the process of gene expression. They are not complex carbohydrate molecules nor are they contributed by the sperm during fertilization. These factors are responsible for controlling which genes are turned on or off by either promoting or inhibiting the transcription process. The mother's regulatory influence on embryonic development through the placenta is separate from the function of transcription factors within the embryo itself. Instead, transcription factors bind to specific gene sequences on the DNA, influencing the activity of RNA polymerase, which is essential for transcription. Furthermore, these proteins respond to environmental stimuli, aiding in the cell’s ability to produce the necessary proteins for its specific function and differentiation. Enhancers and cis-regulatory elements are among the other key components involved in this complex regulation network.