7.2 Transcription 

Initiation

• %%RNA polymerase%% binds to template DNA at promoter (sequence before start of gene) by recognizing TATA (lost of A, T)
• DNA strands are seperated (like helicase)

Elongation

• RNA polymerase synthesizes complementary RNA strands 3’ direction
• no primer necessary
• while DNA is opened, many RNA polymerases may be active synthesizing many RNA strands

Termination

• RNA polymerase recognizes termination sequence and dissociates from DNA

• RNA also dissociates and leaves nucleus via nuclear pores into cytosol

  

Post-Transcription Modifications

• RNA known as pre-mRNA

• Must me modified before it can leave the nucleus

  • addition of poly-A tail
  • prevents degredation

• Removal of introns (non-coding regions) and splicing of exons (coding regions )

  • makes mRNA functional
  • alternative splicing can produce difference mRNAs from the same pre-mRNA