Life 12 - Life Chapter 12 Chapter 12 Life III. How is info...

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Life Chapter 12 Chapter 12 Life III. How is info in DNA transcribed to produce RNA? -transcription requires a DNA template, RNA polymerase and ribonucleotide triphosphates -in DNA, the template strand is transcribed and the non-template strand remains untranscribed A. RNA polymerases share common features RNA polymerases catalyze the synthesis of RNA from template DNA. Catalysis of RNA polymerase occurs in: 1. Enzyme recognition of bases in DNA double helix and bonds 2. Once DNA binds to enzyme, the pincers close, keeping DNA in a double stranded form-closed complex 3. RNA polymerase changes conformation and forms an open complex 4. Open complex makes unpaired bases in DNA available to pair with ribonucleotides and RNA synthesis begins RNA polymerases are processive (binding results in polymerization of hundreds of RNA bases) and they don’t need a primer B. Transcription i. initiation: requires a promeoter (special sequence of DNA, RNA polymerase binds very tightly to) -promoters tell where to start transcription, which DNA strand to transcribe, direction to take. They have initiation sites-where transcription begins ii. elongation: RNA polymerase unwinds DNA about 10 bp at a time and reads strand from 3” to 5”. RNA polymerase also adds new nucleotides to 3” end of growing strand, but is not need for primer to start. RNA transcript is antiparallel to DNA template strand. -errors with RAN are not as harmful because short life span iii. termination: in prokaryotes, translation occurs near 5’ of mRNA before transcription of mRNA is complete. In
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Life 12 - Life Chapter 12 Chapter 12 Life III. How is info...

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