Transcription in Prokaryotes : Transcription in Prokaryotes By Group 13 STEP 1:INITIATION : STEP 1:INITIATION Initiation : Initiation The promoter is in yellow and the terminator is in white. Initiation starts... Initiation : Initiation RNA Polymerase binds to proteins called sigma factors to form a Holoenzyme and initiates transcription...
RNA Polymerase synthesises nucleic acid in the 5’ to 3’ direction and reads it in the 3’ to 5’ direction.
This recognises promoter regions in the DNA. Initiation : Initiation As the RNA polymerase moves down the DNA, the complimentary/
template strand pairs again with the previous stretch of DNA... Initiation : Initiation An Open Complex is formed and the sigma factor dissociates from the holoenzyme. As the DNA is unwound, it becomes
single stranded at the initiation site.
A template for RNA synthesis is formed from
the non-paired deoxyribonucleotides.
Through complementary base pairing,
Ribonucleotides with three phosphate groups
hydrogen bond to the deoxyribonucleotides STEP 2:ELONGATION : STEP 2:ELONGATION Elongation : Elongation Elongation starts... The coding strand is in blue and the template strand is in green Elongation : Elongation The RNA transcript gradually increases in length. Elongation : Elongation During elongation, the RNA Polymerase uses
ATP, GTP, CTP and UTP. STEP 3:TERMINATION : STEP 3:TERMINATION Termination : Termination Termination starts... RNA Polymerase encounters a
stop signal at the end of the gene.
This is also known as a terminator Termination : Termination The completed mRNA drops off the gene
when transcription is complete. Termination : Termination A single gene can be multiplied as a new molecule of RNA Polymerase
can bind to the receptor and start the transcription process all over again...