Final answer:
The TATA box is the component of promoters found in both prokaryotes and eukaryotes. The correct answer is option a).
Step-by-step explanation:
The feature of promoters that can be found in both prokaryotes and eukaryotes is the TATA box. This sequence is A-T rich, which allows the DNA strand to unwind more easily, facilitating the initiation of transcription. In eukaryotes, the TATA box is typically found at positions -25 to -35 relative to the transcription start site.
While in prokaryotes the analogous sequence (the -10 region with consensus sequence TATAAT) is part of the promoter. The TATA box plays a crucial role in transcription initiation across different organisms. This sequence is not identical between prokaryotes and eukaryotes, but its function and its A-T rich nature are conserved.
Other features such as GC boxes or octamer boxes may also be present in eukaryotic promoters but are not universally conserved like the TATA box.