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Before understanding the difference between prokaryotic and eukaryotic transcription, let’s first understand what is transcription. It is the process through which the genetic information in the DNA is copied to an intermediate molecule also known as RNA. in simple words, it is the process of producing RNA molecules from a DNA sequence. This transfer of information is done through the synthesis of the RNA. The RNA keeps the same information as the gene since its sequence is complementary to that of the gene transcribed.
Although the fundamental process and the chemistry behind it remain the same for both, there is a difference between transcription in eukaryotes and prokaryotes. We will compare and contrast prokaryotic and eukaryotic transcription to explain these subtle yet important differences. The Vedantu experts have summarised the differences between the two in an easy to comprehend format. But before pointing out the differences let’s look at the similarities between the two as well.
Similarities Between Prokaryotic and Eukaryotic Transcription
In both kinds of transcriptions, the RNA provides the template for the synthesis.
One strand of DNA duplex acts as the template in both transcriptions.
Both Prokaryotic and Eukaryotic transcriptions produce RNA molecules.
The chemical composition of both transcriptions is similar.
The enzyme RNA polymerase facilitates both kinds of transcriptions.
Now let’s look at the difference between prokaryotic transcription and eukaryotic transcription in detail.
In the case of prokaryotic transcription, both the processes of transcription and translation occur simultaneously and continuously in the cytoplasm. These processes do not occur simultaneously in eukaryotic transcription.
The transcription and translation both occur in the cytoplasm in prokaryotic transcription. However, in eukaryotic transcription, the transcription takes place in the nucleus and the translation occurs in the cytoplasm.
The prokaryotic transcription initiation is simple as the DNA is not associated with the histone protein. In eukaryotic transcription, with the DNA being associated with the protein, the process becomes complex.
The RNA processing takes place in the cytoplasm for prokaryotic transcription and in the nucleus for eukaryotic transcription.
There is only one type of RNA polymerase enzyme in prokaryotic transcription and it helps to synthesize all the other types of RNA in the cells ( mRNA, tRNA, and rRNA). Eukaryotic transcription involves three types of RNA. There is RNA Polymerase I that helps in the rRNA synthesis, RNA Polymerase II for mRNA, and RNA Polymerase III that aids in the synthesis of tRNA and 5S rRNA.
RNA Polymerase Composition
RNA polymerase in prokaryotic transcription has 5 polypeptides. In eukaryotic transcription, RNA polymerase I have 14 subunits, and RNA polymerase II has 10-12 subunits.
Location of the Promoter Region
The promoter region is located upstream to the start site in both kinds of transcriptions but in eukaryotic transcription, sometimes, the promoter region is located downstream to the start site in RNA Polymerase III (present only in eukaryotic transcription).
One of the critical prokaryotic and eukaryotic transcription difference lies in the presence of the σ factor. Prokaryotic transcription initiation requires the presence of σ factor which is not present in eukaryotic transcription which requires initiation factors.
Binding of the RNA with the Promoter Region
In prokaryotic transcription, the RNA polymerase recognizes and binds with the promoter region with the help of the σ factor. This is possible in eukaryotic transcription only when the initiation factors are present in the promoter region.
Presence of TATA Box, CAT Box, and Pribnow Box
While the Pribnow boxes are present at 10 locations in the case of prokaryotic transcription, they are absent in eukaryotic transcription. TATA boxes and CAT boxes are not present in the promoter region in case of prokaryotic transcription and the Pribnow box is the sequence that is considered functionally equivalent to the TATA box. In eukaryotic transcription, TATA boxes are present 25-35 base pairs before the start of the transcription initiation site of a gene.
Introns are absent in prokaryotic transcription and thus there is no splicing of mRNA. As they are present in eukaryotic transcription, splicing is also present.
Modification of the Primary Transcript
An essential difference between prokaryotic and eukaryotic transcription is that the primary transcript does not undergo any post-transcriptional modification in prokaryotic transcription but it happens in the case of eukaryotic transcription.
When we differentiate between prokaryotic and eukaryotic transcription, one of the essential points to consider is the RNA capping. It is absent in prokaryotic transcription and the mRNA does not have a 5’ guanosine cap. On the other hand, eukaryotic transcription includes RNA capping that takes place at the 5’ position mRNA.