Difference between Prokaryotic & Eukaryotic Transcription

Transcription in Prokaryotes and Eukaryotes

Transcription is a process by which the genetic information present in the DNA is copied to an intermediate molecule (RNA). The sequence in the RNA is complementary to that of the gene which is transcribed and thus the RNA retains the same information as the gene itself. Transcription is a universal process in the living word and it occurs both in prokaryotes and eukaryotes.  Even though the overall process of transcription is similar in both prokaryotes and eukaryotes, there do exists some fundamental differences between these groups. This post summarizes the overall similarities and differences between the Prokaryotic and Eukaryotic transcription in a detailed but easy way.

Similarities between prokaryotic and eukaryotic transcription

1.      In both groups DNA acts as the template for RNA synthesis

2.      In both groups transcription produces RNA molecule

3.      Chemical composition of transcript is similar in both groups

4.      Transcription is facilitated by the enzyme RNA polymerase in both groups

5.      In both groups, one strand of the DNA duplex acts as the template

Difference between prokaryotic and eukaryotic transcription

Sl. No.Prokaryotic TranscriptionEukaryotic Transcription
1Transcription and translation are continuous process and occurs simultaneously in the cytoplasmThey are two separate processes, transcription occurs in the nucleus whereas translation occurs in the cytoplasm
2Transcription initiation machinery is simple since DNA is not associated with any histone proteinsTranscription initiation machinery is very complex since the genetic material is associated with proteins
3Only one type of RNA polymerase enzyme, which synthesize all types of RNA in the cell (mRNA, rRNA and tRNA)Three types of RNA polymerase in the cell. RNA Polymerase I for rRNA synthesis RNA Polymerase II for mRNA synthesis. RNA polymerase III for tRNA and 5S rRNA synthesis
4RNA polymerase with 5 subunits, Two α subunits, One β subunit, One β’ subunit, One ω subunit. Functional RNA polymerase is 2α1β1β’ωRNA polymerase I with 14 subunits, RNA polymerase II with 10 -12 subunits, RNA polymerase II with 12 subunits
5σ factor present, which is essential for transcription initiationσ absent and it is not required for transcription initiation. Initiation of transcription is facilitated by initiation factors
6RNA polymerase can recognize and bind to the promoter region with the help of σ factorRNA polymerase cannot recognize the promoter region directly unless the promoter is pre-occupied by transcription initiation factors.
7Promoter region always located upstream to the start sitePromoter region usually located upstream to the start site, but rarely as in the case of RNA polymerase III, promoter is located downstream to start site
8Promoter region contain pribnow box at -10 positions. TATA box and CAT box are absent in the promoter region of prokaryotesPromoter region contains; TATA box located 35 to 25 upstream; CAT box located ~ 70 nucleotide upstream; GC box located ~ 110 nucleotide upstream. Pribnow box absent in eukaryotes
9Termination of transcription is done either by rho dependent mechanisms or rho independent mechanismsA termination mechanism of transcription is not completely known. It may be direct by the poly A signal or by the presence of termination sequence in the DNA
10Usually there is no post transcriptional modification of the primary transcriptPrimary transcript undergo post transcriptional modifications (RNA editing)
11RNA capping absent, mRNA is devoid of 5’ guanosine capRNA capping present, capping occurs at the 5’ position of mRNA
12Poly A tailing of mRNA is absentMature mRNA with a poly A tail at the 3’ position. Poly A tail is added enzymatically without the complementary strand
13Introns absent in the mRNAIntrons present in the primary transcript
14Splicing of mRNA absent since introns are absentSplicing present, introns in the primary transcript are removed and exons are rejoined by a variety of splicing mechanisms
15Genes usually polycistronic and hence single transcript may contain sequence for many polypeptidesGenes are monocistronic thus single transcript code for only one polypeptide
16SD sequence (Shine-Dalgarno sequence) present about 8 nucleotide upstream of start codon in the mRNA, SD sequence act as the ribosome binding siteSD sequence is absent in mRNA of prokaryotes

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