Final answer:
Eukaryotic promoters can span variable regions across the DNA, containing elements such as the CAAT box, GC-rich boxes, and the TATA box, important for binding the preinitiation complex and initiating transcription.
Step-by-step explanation:
In eukaryotic cells, promoters can vary greatly in terms of their length and composition. These regions may contain several conserved elements such as the CAAT box (GGCCAATCT) at approximately -80 bases, and further upstream, various GC-rich boxes (GGCG) or octamer boxes (ATTTGCAT) can be present. Promoters have been found within genes, far upstream, or sometimes even downstream of the genes they regulate.
Core promoter sequences can bind the preinitiation complex, which is necessary for transcription initiation. Among the consensus sequences, the TATA box serves as a vital component of the promoter region in eukaryotes, with a sequence TATAAA located at -25 to -35 bases from the initiation site, aiding in the unwinding of DNA due to A-T bonds' low thermostability.