Final answer:
Eukaryotic genes are primarily controlled at the level of transcription initiation, with transcription factors recruiting RNA polymerase to the promoter region and epigenetic modifications influencing chromatin accessibility.
Step-by-step explanation:
The majority of eukaryotic genes are controlled at the level of transcription initiation. This is because gene expression in eukaryotes involves various complex mechanisms that determine when, where, and how much of a gene's product is made. In eukaryotic cells, transcription initiation requires the assembly of general transcription factors and the recruitment of RNA polymerase to the promoter region of a gene. This is facilitated by the interaction of transcription factors with the promoter region to control the transcription of the target gene. Additional regulatory mechanisms involve epigenetic modifications that affect the accessibility to the chromatin structure and thus influence gene expression. Furthermore, there are mechanisms to regulate gene expression at post-transcriptional, translational, and post-translational levels, involving mRNA processing, nuclear shuttling, degradation, translation initiation, and modifications to the synthesized proteins. Therefore, while both prokaryotes and eukaryotes regulate gene expression at multiple stages, eukaryotes exhibit a higher level of complexity and commonly regulate gene expression at the stage of transcription initiation.