Final answer:
Transcription involves differences between bacteria and eukaryotes due to the eukaryotic nucleus and more complex gene regulation. Bacterial mRNAs are polycistronic and translation can commence during transcription, while eukaryotic mRNAs are usually monocistronic and undergo extensive processing within the nucleus before translation.
Step-by-step explanation:
The molecular processes of transcription and its regulation differ between bacteria (prokaryotes) and eukaryotes, largely due to structural and compartmentalization differences.
In bacteria, transcription occurs in the cytoplasm since there is no nucleus, and the DNA is not as complexly organized as in eukaryotes. Bacterial RNA polymerase transcribes mRNA directly, and these mRNAs are often polycistronic, meaning they can encode multiple proteins. Additionally, the association of ribosomes with mRNA to start translation can happen even before transcription is completed.
Conversely, eukaryotes employ three different RNA polymerases where each transcribes a different subset of genes. Eukaryotic mRNA is usually monocistronic, specifying a single protein. Transcription occurs within the nucleus amidst chromatin and undergoes extensive processing before the mature mRNA is exported to the cytoplasm for translation. This processing includes 5' capping, splicing out of introns, and polyadenylation at the 3' end.
The differences in transcription between prokaryotes and eukaryotes are a result of evolutionary pressures that led to more complex regulatory mechanisms, possibly to manage the increased complexity of eukaryotic organisms and their multicellular functions.