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Chapter 12 Gene Expression…

- - - - STEPS:
        
        Capping: modified guanosine attached to 5` end. NEEDED: so mRNA can exit nucleus+ bind ribosome.
        
        100-200 adenine nucleotides added to 3` end (not encoded ). * increase lifespan+ stability. Bacteria (may DESTABLIZE mRNA).
        
        Splicing.
        
        introns removed, exons remains(coding sequence in mature mRNA).
        
        BY: Spliceosome (compose of snRNPs)
        
        snRNPs= small nuclear RNA + proteins
        
        splicing occur several ways=produce different product. (Alternative splicing).
        
        rRNA & tRNA.
        are ribozymes=self-splicing
  - - - RNA polymerase reach terminator = it+ RNA transcript dissociate from DNA.
    - - RNA polymerase use non-coding strand (read 3to 5)to synthesize mRNA
        U substituted for T.
        synthesize 5to 3.
      - sigma factor released
- - - - charged tRNA binds to A site, polypeptide from tRNA in P site go to A site.(peptidyl transfer reaction).
        
        reribosome translocate 1 codon to the right /uncharged tRNA released from E site (this continues until a stop codon is reached).
  - - - completed polypeptide is attached to tRNA in P and stop codon in A sites.
        release factor: bind to stop codon in A site. polypeptide: released in P site (bond is hydrolyzed between it and tRNA)
        tRNA is released.
        mRNA+ ribosomal subunit+ releas factor: dissociate