1. Location:
- Prokaryotes: Transcription occurs in the cytoplasm, as prokaryotes lack a nucleus.
- Eukaryotes: Transcription takes place in the nucleus, where the DNA is housed.
2. RNA processing:
- Prokaryotes: mRNA is produced directly from the DNA template and can be translated into protein immediately. There is minimal RNA processing.
- Eukaryotes: The initial transcript, called pre-mRNA, undergoes significant processing before it can be translated. This includes:
* Capping: Addition of a 5' cap to protect the mRNA from degradation and help with ribosome binding.
* Splicing: Removal of non-coding regions called introns.
* Polyadenylation: Addition of a poly-A tail to the 3' end for stability and export from the nucleus.
3. Transcription factors:
- Prokaryotes: Transcription is controlled by a single RNA polymerase and a few transcription factors that bind directly to the promoter region of the gene.
- Eukaryotes: Transcription is regulated by multiple RNA polymerases (I, II, and III), and a complex interplay of transcription factors (general and specific) that bind to the promoter and enhancer regions of the gene. This allows for more precise and elaborate control of gene expression.
