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Difference Between Prokaryotic and Eukaryotic Transcription

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Know the Difference Between Prokaryotic and Eukaryotic Transcription

Before understanding the difference between prokaryotic and eukaryotic transcription, let’s first understand what transcription is. 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.

 

  • Process Timing

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.

 

  • Process Location

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.

 

  • Genetic Association

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.

 

  • RNA Processing

The RNA processing takes place in the cytoplasm for prokaryotic transcription and in the nucleus for eukaryotic transcription.

 

  • Types of RNA

There is only one type of RNA polymerase enzyme in prokaryotic transcription and it helps to synthesise 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).

 

  • Presence of σ Factor

One of the critical prokaryotic and eukaryotic transcription differences 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.

 

  • Presence of Introns

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.

  • RNA Capping

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.


What is Transcription ?

Transcription is a very important process for the Reproduction and Evolution of life on the earth. In this process the Deoxyribonucleic Acid or DNA which is a double strand polymer chain develops from the single strand polymer chain called RNA or Ribonucleic Acid. DNA is the blueprint of the life form for the organism that carries the genetic information inherited from its parents. In this process RNA is also synthesised and provides the template for the further development of DNA. During the development of organisms RNA molecules are produced from the DNA sequence.


This process may sound identical for all cases but it is significantly distinct for Transcription in eukaryotes and prokaryotes. Eukaryotes are the uniCellular organisms without any definite structure or Cell organelles. Bacteria are a good example of Eukaryotic organisms. while Prokaryotic organisms are the higher version with a well structured Cell and Cell organelles. Prokaryotic Cell organisms are widely available in the organisms of one Cell to multiCellular or complex organisms.


The main difference between Eukaryotic Transcription and Prokaryotic Transcription is that the RNA capping is absent in Prokaryotic Cells. In the Transcription in Eukaryotic Cells the capping takes place at the 5' position mRNA which is not present in the Prokaryotic Cell.  In Eukaryotic Cells the cytoplasm and nucleus are the area where the RNA processing takes place in different times. While in the Prokaryotic Cells the both processing takes place simultaneously. Another major difference is the involvement of the σ factor for initiation of Transcription in Prokaryotic Cells that is absent in Eukaryotic Cells.


There are also some similarities between the Eukaryotic and Prokaryotic RNA Transcription. The chemical reaction and processes are similar in nature in both Cells and the end product is RNA molecules in both cases.

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FAQs on Difference Between Prokaryotic and Eukaryotic Transcription

1. What are the primary differences between transcription in prokaryotic and eukaryotic cells?

The main differences between prokaryotic and eukaryotic transcription lie in their location, complexity, and coupling with translation. Key distinctions include:

  • Location: Prokaryotic transcription occurs in the cytoplasm, while eukaryotic transcription takes place in the nucleus.
  • Enzymes: Prokaryotes use a single RNA polymerase for all RNA synthesis. Eukaryotes use three distinct types: RNA Polymerase I, II, and III.
  • Gene Structure: Prokaryotic genes are often polycistronic (one mRNA codes for multiple proteins), whereas eukaryotic genes are monocistronic (one mRNA for one protein).
  • Initiation: Prokaryotes use a sigma factor to recognise promoter sequences like the Pribnow box. Eukaryotes use a complex set of general transcription factors to bind to promoter elements like the TATA box.
  • RNA Processing: Eukaryotic mRNA undergoes extensive processing (splicing, 5' capping, and 3' polyadenylation), but prokaryotic mRNA does not.

2. Why does eukaryotic mRNA require processing after transcription, but prokaryotic mRNA does not?

Eukaryotic mRNA requires processing to become mature and functional for three main reasons. First, splicing removes non-coding regions called introns. Second, a 5' cap is added to protect the mRNA from degradation and to help ribosomes bind for translation. Third, a poly-A tail is added to the 3' end, which increases stability and aids in its export from the nucleus. In contrast, prokaryotic mRNA lacks introns and transcription is directly coupled with translation in the cytoplasm, meaning ribosomes start translating the mRNA while it is still being synthesised. This immediate translation makes extensive processing both unnecessary and impossible.

3. How do the roles of transcription factors differ between prokaryotes and eukaryotes?

In prokaryotes, the primary transcription factor is the sigma (σ) factor. Its role is simple: it binds to the RNA polymerase and directs it to the specific promoter region of a gene to initiate transcription. In eukaryotes, the system is far more complex. They use a set of general transcription factors (GTFs) that are required at every promoter to help RNA Polymerase II bind and form the pre-initiation complex. Additionally, eukaryotes have thousands of specific transcription factors that bind to distant DNA sequences (enhancers or silencers) to precisely regulate the rate and timing of transcription in response to developmental or environmental cues.

4. What is the significance of the TATA box in eukaryotic transcription compared to prokaryotic initiation?

The TATA box is a crucial DNA sequence found in the core promoter region of many eukaryotic genes. Its primary significance is serving as a binding site for the TATA-binding protein (TBP), a component of the general transcription factor TFIID. This binding event is a key step in assembling the entire transcription pre-initiation complex, which positions RNA Polymerase II correctly to start transcription. In prokaryotes, the functionally equivalent sequence is the Pribnow box (or -10 sequence), which is directly recognised by the sigma factor associated with RNA polymerase, making the initiation process more direct and less complex.

5. Where does transcription occur in prokaryotic versus eukaryotic cells, and why is this location significant?

In a prokaryotic cell, transcription occurs in the cytoplasm because there is no nucleus. In a eukaryotic cell, transcription happens inside the nucleus. This difference in location is highly significant. In prokaryotes, the absence of a nuclear barrier allows for transcription-translation coupling, where ribosomes can attach to the emerging mRNA strand and begin protein synthesis immediately. In eukaryotes, the physical separation of the nucleus (transcription) and cytoplasm (translation) allows for essential RNA processing steps like splicing and capping to occur before the mature mRNA is exported for translation, enabling more complex gene regulation.

6. Why are prokaryotic genes often organised into operons (polycistronic), while eukaryotic genes are typically monocistronic?

Prokaryotic genes are often organised into operons, leading to polycistronic mRNA, because it provides an efficient way to control related genes. All genes in an operon, which typically code for proteins involved in the same metabolic pathway, are transcribed together under the control of a single promoter. This ensures that all necessary proteins are produced simultaneously when needed. Eukaryotic genes are monocistronic, allowing for more complex and individualised regulation. This fine-tuned control is essential for the development and function of different cell types in multicellular organisms, where different genes need to be expressed at different times and levels.

7. How does the type of RNA polymerase enzyme differ in prokaryotic and eukaryotic transcription?

The RNA polymerase enzymes used in transcription are a key point of difference. Prokaryotes utilise a single type of RNA polymerase to synthesise all forms of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). In contrast, eukaryotes have three distinct and specialised enzymes:

  • RNA Polymerase I: Synthesises most of the rRNA.
  • RNA Polymerase II: Synthesises all protein-coding mRNA and some small nuclear RNAs.
  • RNA Polymerase III: Synthesises tRNA, 5S rRNA, and other small RNAs.

This division of labour in eukaryotes reflects the greater complexity of their gene expression and regulation.