Genetics is a branch of biology that deals with the study of genes, genetic variations, and hereditary in living organisms. The discipline is wide and complex to understand.
Transcription is one of the ways in which genetic information is conveyed. Therefore, transcription is the process where genetic information is copied from DNA templates to RNA molecules.
Transcription is a universal process. It occurs in both eukaryotes and prokaryotes. The overall process in each organism is the same. But there exist some fundamental differences.
So, what is the main difference between prokaryotic and eukaryotic transcription? Prokaryotic transcription takes place in the cell cytoplasm and eukaryotic transcription occurs in the cell nucleus.
According to biology, genetic information in the DNA is copied to a messenger RNA. The mRNA is usually transported in the cytoplasm and translated into a functional protein molecule.
The crucial components for transcription are DNA template, ribonucleoside triphosphate, and transcription apparatus. The process consists of three stages such as initial, elongation, and termination.
The article provides a detailed explanation of the similarities and differences between prokaryotic and eukaryotic transcription. Let’s find that out together now:
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Comparison Table (Prokaryotic Transcription vs Eukaryotic Transcription)
|Basic Terms||Prokaryotic Transcription||Eukaryotic Transcription|
|Meaning||It is a continuous process that takes place in the cytoplasm.||It is a process that occurs in the cell nucleus.|
|Initiation Machinery||Quite simple. DNA not associated with histone proteins.||Quite complex. Genetic materials are associated with proteins.|
|Type of RNA polymerase Enzyme||One type only. It is responsible for the synthesis of mRNA, tRNA, and rRNA.||Three types present:
|RNA Polymerase Subunits||5 subunits||RNA Polymerase:
|Alpha Factor||Present. Essential for transcription initiation.||Absent. Initiation factors enhance transcription.|
|Promoter Recognition||RNA polymerase recognizes and binds to the promoter region with the help of the alpha factor.||Not easily recognized by the RNA polymerase. The pre-occupied transcription initiation factor makes the promoter region recognizable.|
|Promoter Location||Upstream to the start site.||Downstream to the start site.|
|Promoter Region Composition||Pribnow box at -10 position.||TATA box at 30-25 upstream.
CAT box at -70 nucleotides upstream.
GC box at -110 nucleotides upstream.
|Termination Mechanism||Done by either Rho-dependent mechanism or rho independent mechanism.||Either by direct poly-A signal or presence of termination sequence in DNA.|
|Primary Transcript Modification||No post transcription modification.||Primary transcript undergoes post transcription modification for RNA editing.|
|RNA Clapping||Absent. But mRNA is devoid at 5 guanosine caps.||Present. Occurs at the 5th position of mRNA.|
|Poly A Tailing||mRNA absent.||mRNA present at the 3rd position.|
|Introns||Absent in mRNA.||Present in the primary transcript.|
|Gene Structure||Polycistronic. Single transcript may contain sequences for many polypeptides.||Monocistronic. Single transcript coded for only one polypeptide.|
|Splicing of mRNA||Absent||Present|
|SD sequence||Present. It acts as a ribosome binding site.||Absent.|
|Transcription and Translation||Occur simultaneously.||Differ in space and time.|
|Enhancement of Proteins||Absent||Present|
|Inhibitors||Rifampin: RNA polymerase binds to β subunit.
Actinomycin-Intercalates to interrupt transcription.
|α amanitin: Inhibits RNA polymerase 2 most strongly|
What Is Prokaryotic Transcription?
Prokaryotic organisms do not have an organized nucleus. The genetic materials are suspended in the cell cytoplasm. All the precursors needed for transcription are located in the cytoplasm. Prokaryotic transcription usually happens in the cytoplasm. The process needs an RNA polymerase enzyme for transcription to be successful.
The RNA polymerase enzyme contains five subunits. The enzyme usually binds to the stigma and promoter to initiate transcription in the holoenzyme.
Keep in mind that the prokaryotes’ DNA is not bound to histone. The transcription process is not initiated at all since it happens directly. It is ideal for those prokaryotes with overlapping genes.
Prokaryotic transcription starts at the promoter region, elongates via the coding region, and ends when the RNA polymerase enzyme reads the termination signal.
Prokaryotes have two types of termination signals. Rho dependent and independent termination signal. Transcribe mRNA will be translated during the transcription process.
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What Is Eukaryotic Transcription?
Eukaryotes have a more organized cell nucleus. It makes the transcription process more complex and takes place in the cell nucleus.
Eukaryotes have five types of RNA polymerase ideal for transcription. It also contains 10-17 subunits of the foster transcription process.
Eukaryotes DNA usually detaches from the histone and unwind near the promoter region. The RNA polymerase and enhancers will be bound on the promoter region.
Eukaryotic transcription starts at the transcription initiation site and ends at the transcription termination signal. The transcript is usually long and undergoes several extensive processing.
Pre-mRNA occurs due to slicing out of the non-coding region and the coding region gets joined back together to form a mature mRNA. It is already translated.
Main Differences between Prokaryotic and Eukaryotic Transcription
- Prokaryotic transcription occurs in the cytoplasm. Eukaryotic transcription occurs in the cell nucleus.
- Prokaryotic translation and transcription occur simultaneously. Eukaryotic translation and transcription occur in different spaces and times.
- Prokaryotic transcription RNA gets released and processed in the cytoplasm. Eukaryotic transcription RNA gets released and processed in the cell nucleus.
- Prokaryotic transcription RNA polymerase has five polypeptides. Eukaryotic transcription RNA polymerase has 10-15 polypeptides.
- Prokaryotic transcription does not need enhancers. Eukaryotic transcription needs initiators for transcription to take place.
- Prokaryotic transcription mRNA transcript has fewer surplus nucleosides. Eukaryotic transcription mRNA transcript has numerous surplus nucleosides.
- The prokaryotic transcription promoter region is located upstream. The eukaryotic transcription promoter region is located downstream.
- The prokaryotic transcription promoter region contains the Pribnow box. The eukaryotic transcription promoter region contains TATA and CAT boxes.
- Prokaryotic transcription termination has either rho dependent or rho independent. Eukaryotic transcription has a direct poly-A termination signal.
- Prokaryotic transcription lacks introns. Eukaryotic transcription has introns in the primary transcript.
Similarities between Prokaryotic and Eukaryotic Transcription
- Both DNA templates are for RNA synthesis.
- Both transcriptions produce RNA molecules.
- Both have similar chemical compositions to the primary transcript.
- Both transcription process is facilitated by an RNA polymerase enzyme.
- One strand of DNA duplex act as a template in both groups.
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The main difference between prokaryotic transcription and eukaryotic transcription depends on the location of occurrence. Prokaryotic transcription happens in the cytoplasm and eukaryotic transcription occurs in the nucleus.
Prokaryotes are the lower organisms with unorganized nuclei and eukaryotes are higher organisms with the organized cell nucleus. Both transcriptions have DNA templates for RNA synthesis. Besides that, the process is enhanced by an RNA polymerase enzyme.
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