Initiation of transcription occurs when DNA is opened and promoters and sigma factors bind to the promoter regions of genes that need to be transcribed.
RNA polymerase binds the promoter region which is slightly upstream of the gene site. Its binding is facilitated by the promoters and sigma factors.
Elongation is the extension of that bubble while RNA polymerase is zipping along the DNA, coding an RNA complementary strand of the desired genes.
The DNA opens via helicase enzymes which create a transcription bubble.
RNA polymerase reads DNA in the 3' to 5' direction, such that the new strand is synthesized in the 5' to 3' direction, just like DNA replication.
Nucleotides are added to the 3' end of the growing mRNA molecule, such that the 3' end is being extended while the 5' end is fixed.
Termination of transcription occurs once the gene is finished and can happen in multiple ways.
A stem loop, or hairpin loop, puts mechanical stress on the DNA RNA temporary bond, which can pull the strands apart and release RNA polymerase.
Rho proteins can also directly bump RNA polymerase off the DNA strand, allowing the RNA strand to be read for translation and the DNA strand to recoil.
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