Distinguish between transcription in prokaryotes and eukaryotes
Bacteria are monocistronic or polycistronic (number of polypeptides encoded per mRNA). Strand elongation is done by a holoenzyme.Eukaryotes are exclusively monocistronic. Strand elongation is performed by RNA polymerase 1, 2, and 3.
Transcription is the process of synthesizing a complementary RNA strand from a DNA template strand. There are significant differences in the transcription process between prokaryotes and eukaryotes.
In prokaryotes, the transcription process occurs in the cytoplasm because there is no real distinction between the genetic material (DNA) and the cytoplasm. One RNA polymerase is responsible for transcribing all the types of RNA needed for protein synthesis as well as other cellular processes. Prokaryotic promoter sequences are located upstream of the gene, which is usually preceded by a Shine-Dalgarno sequence, the ribosome-binding site, that facilitates translation. Prokaryotic mRNA is usually polycistronic, meaning that it codes for several genes arranged as an operon or a cluster. The transcription and translation process in prokaryotes are almost simultaneous.
On the other hand, eukaryotic transcription occurs in the nucleus because there is a clear separation between the genetic material (DNA) and the cytoplasm. Eukaryotic transcription is more complex than prokaryotic transcription because mRNA undergoes various modifications such as splicing, capping and polyadenylation before the final functional mRNA is produced. Eukaryotes have three types of RNA polymerases, each responsible for a particular type of RNA: RNA polymerase I transcribes rRNA, RNA polymerase II transcribes mRNA, and RNA polymerase III transcribes tRNA and other small RNAs. The primary transcript in eukaryotes is monocistronic, meaning that it usually encodes for a single gene, and transcriptional and translational processes are separated. Eukaryotic mRNA requires significant processing steps before leaving the nucleus and entering the cytoplasm for translation.
Overall, transcription in prokaryotes is simpler, occurs in the cytoplasm, and the mRNA is usually polycistronic, while transcription in eukaryotes is more complex, occurs in the nucleus, and mRNA is usually monocistronic.
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