Notes: RNA Polymerase / Transcription Steps

Transcription and Translation:  Transcription
transcription, processing, and translation

RNA polymerase
     in bacteria 1 type
     in eukaryotes 3 specialized types (mRNA = RNA polymerase II; 40.000 in a human cell)

STEPS IN TRANSCRIPTION

Step Number:

Explanation:

1

 RNA polymerase binds to regions--called promoters.

The promoter includes the initiation site and dozens of nucleotides "upstream."  Certain regions of the promoter are especially important for recognition by RNA polymerase.

example:  RNA poly II keys on TATA box (segment of DNA rich in T and A bases) about 25 nucleotides upstream from initiation site.

*** Transcription factors aid polymerases in this search for promoter regions.  One type is a protein that binds to the promoter.  RNA poly II recognizes and goes to work there. ***

2

 RNA poly untwists one twist @ a time, adds nucleotides to the 3' end of the growing RNA molecule.  Afterwards mRNA peels away from the template.

RNA poly can transcribe 60 nucleotides per second (nps).

*** Bulk transcription yields bulk proteins ***

3

 Termination site is usually AATAAA in eukaryotes (then comes RNA processing).

Next:  "Translation and RNA Processing."