Question

How does transcription in prokaryotic cells differ from transcription in eukaryotic cells? List at least ten transcriptional processes (from primary transcript to mature RNA molecule) that eukaryotes need but prokaryotes do not.

Answer 1

Transcription is a process by which the genetic information present in the DNA is copied to an intermediate molecule (RNA). Transcription is a universal process in the living word and it occurs both in prokaryotes and eukaryotes.

the major events of transcription are common in both prokaryotes and eukaryotes but little complex in eukaryotes

transcription in prokaryotes vs transcription in eukaryotes

DNA dependent RNA polymerase synthesizes the RNA in prokaryotes,RNa polymerase of e coli is a complex holoenzyme with five polypeptides aolng with sigma factor and whereas in eukaryotes RNA polymerase synthesizes the RNA in eukaryotes RNA polymerase is exist in 3 types RNa pol 1 for r RNA,RNA pol2 for m RNA and RNA pol3 codes for t RNA

prokaryotic intiation:at promoter region ( TATA box /pribnow box) DNA and enzyme binds and start RNA synthesis, eukaryotic intiation: enzyme and DNA binds at promoter region called hogness box and also transcription factors (transcription factors D,A,B,F,E,H)also attaches and stimulates transcription by enhancers

prokaryotic elongation:as the holoenzyme RNA polymerase recognise the promoter ,sigma factor is released,and transcription proceeds,RNA synthesizes by using ATP,Gtp, CTP and utp)

eukaryotic elongation: binding of transcription factors promotes RNA synthesis,from 5'end to 3'

prokaryoticTermination : termination by rho factor ,rho factor binds to growing RNA and act as ATPase and terminate transcription and release RNA and also by Rho independent termination by formation of hair hoop structure.

eukaryotic termination: occurs by termination sequence or signal or factor dependent termination.

TRANSCRIPTIONAL FACTORS REQUIRED ONLY BY EUKARYOTES ARE FOLLOWING

1. Transcriptional factors 2. 3 different types of RNA polymerase enzymes 3.poly A tail signal 4.post transcriptional process 5.M RNA editing 6.splicing removal of introns 7.5' capping 8.other enzymes 9.SD sequence (Shine-Dalgarno sequence) present about 8 nucleotide upstream of start codon