Transcription:

This is a process in which the information from a DNA strand is copied into messenger RNA (m-RNA). It describes how a DNA Strand is converted into RNA (m-RNA). This is a process of the central dogma. To understand the difference between prokaryotic and eukaryotic transcription first we must know about what transcription is and how the process works. You can find out the summary of transcription on the page (Go to the page) ….

WHY IS THE PROCESS OF TRANSCRIPTION MORE COMPLICATED IN EUKARYOTES THAN PROKARYOTES?

Some reasons by which we can differentiate the prokaryotic and eukaryotic transcription are listed here:

• In eukaryotes, the nuclear envelope is well developed due to which RNA must reach the cytoplasm through nucleopore to form proteins.
• Another complexity is the presence of three types of RNA.

• *m-RNA (catalyzed by RNA polymerase 2)
• *t-RNA (catalyzed by RNA polymerase3)
• *rRNA (catalyzed by RNA polymerase 1)

• The conversion of Hn-RNA to mature messenger RNA by the process of splicing, capping and tailing is another task that must be done within the eukaryotes.
• [Hn-RNA is heterogeneous nuclear RNA].
• Where prokaryotes contain only 3 different promoters: -10, -35 promoter, and upstream elements, eukaryotes contain different promoters: initiator elements, TATA box, CAAT box, promoter elements.
• In prokaryotes, the process of transcription and translation occurs simultaneously. In eukaryotes 1^st the RNA is transcribed in the nucleus and translated in the cytoplasm (after the transcription).
• Termination in prokaryotes done by a rho-independent or rho-dependent process. While in prokaryotes termination is occur by Poly A tail signal and downstream terminator sequence.

Prokaryotes vs Eukaryotes (Translation)

S.NO	Prokaryotes	Eukaryotes
1	Methionine (the initiating amino acid) needs to be formulated (Due to the existence of two tRNA for methionine).	Methionine is not formulated because there is only one tRNA present for methionine.
2.	In prokaryotes, ribosomes arrive at the mRNA at AUG codon or nearby Shine-Dalgarno site.	Ribosomes arrivers at the 5` end of mRNA.
3.	Initiation factors are not needed to create initial contact between ribosomes and mRNA	Many protein factors along with ATP are needed to engage mRNA for ribosomes.
4.	Small units (the 30s) of the ribosome can also engage mRNA before binding of initiator methionine	Small units (the 40s) of ribosomes bind to mRNA after initiator methionine binds to the tRNA.

The process of splicing capping and tailing is another process which will be discussed later.