Transcription in Prokaryotes & Eukaryotes

Transcription in Prokaryotes & Eukaryotes

Gene Expression

? There are 4 major events that occur during the process of gene expression

? Transcription ? RNA processing ? Translation ? Protein processing

A Gene is a Transcription Unit

Promoter

Regulatory sequence

Terminator

DNA

Transcription

mRNA 5

Start codon

Ribosomalbinding site

Many codons

3

Stop codon

Prokaryotic Gene Structure

+1

DNA Cis-Regulatory Elements

ShineDelgarno

box ATG

Stop Codon TAA, TAG,

TGA

Coding Sequence = ORF 1

ShineDelgarno

box ATG

Stop Codon

Coding Sequence = ORF 2

USE/Promoter /Operator

5' UTR = Leader Protein A sequence

Cistron 1

Spacer = 5'UTR of 2nd cistron

Protein B

Cistron 2

Regulatory Sequences Structural or Coding Sequences

Termination sequence

Regulatory and Coding Sequence Unit = Operon

Polycistronic structure

Prokaryotic Gene Structure

DNA

+1

Cis-Regulatory Elements

Shine-Delgarno box ATG

Shine-Delgarno

Stop Codon box

TAA, TAG, TGA

ATG

Stop Codon TAA, TAG, TGA

Coding Sequence= ORF

Coding Sequence= ORF

USE/Promoter /Operator

5' UTR = Leader sequence

Protein A

Cistron 1

Spacer = 5'UTR of 2nd cistron

Protein B Cistron 2

Terminator sequence

5' UTR = Leader sequence

Spacer

Polycistronic

mRNA

ORF Protein A

+1

AUG

Shine-Delgarno

box

Stop Codon

AUG Shine-Delgarno

UAA, UAG, UGA

box

ORF Protein B

Stop Codon UAA, UAG, UGA

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