STEPS OF TRANSCRIPTION

1-  Initiation of transcription

RNA polymerase enzyme binds promoter region of DNA . The specific site for the enzyme binding is called TATA BOX .

The double stranded DNA unwinds .

The sigma factor initiate the process .

The first nucleotide binds to the enzyme complex .

The sigma factor is released from core enzyme 

2- Elongation of RNA chain 

The elongation is the function of RNA polymerase core enzyme .

The enzymes moves on DNA template .

Nucleotides added at OH-- end of nucleotide to form a new RNA strand , and one pyrophosphate is released for each nucleotide added .

The average speed of transcription is 40 nucleotides per second.

The RNA chain grows in the 5' - 3' direction .

3 - RNA chain termination

Two mechanisms are well known . They are

I- Intrinsic termination 

It is also called Rho independent termination .

The RNA polymerase recognise a palindrome sequence  of on DNA that from a hair pin loop on the RNA chain .

Therefore , it dissociates from the DNA.  

II- Rho dependent termination 

This uses a protein called p.

The Rho protein stops RNA synthesis at specific sites .