Chapter_17_From_Gene_to_Protein

Chapter_17_From_Gene_to_Protein - Ch. 17: Gene to Protein...

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Ch. 17: Gene to Protein The three main processes linking gene to protein are: Transcription RNA Processing Translation Transcription Transcription is the process by which RNA is synthesized from a DNA template in the nucleus of a cell. The enzyme responsible for transcription is RNA polymerase , which moves along a gene from its promoter to just beyond its terminator. Like the DNA polymerase that function in DNA replication, RNA polymerases can add nucleotides only to the 3’ end of the growing polymer. Thus, an RNA molecule elongates in its 5’ to 3’ direction (Campbell 300). As RNA polymerase moves along the DNA, it continues to untwist the double helix, exposing about 10-20 DNA bases at a time for pairing with RNA nucleotides. The enzyme adds nucleotides to the 3’ end of the growing RNA molecule as it continues along the double helix. In the wake of this advancing wave of RNA synthesis, the DNA helix re-forms and the new (pre- mRNA) molecule peels away from its DNA template. RNA Processing Before RNA processing, enzymes modify the two ends of a eukaryotic pre-mRNA molecule. A cap consisting of a modified guanosine triphosphate is added to the 5’ end of the RNA as soon as it is made. A poly (A) tail consisting of up to 200 adenine nucleotides is attached to the 3’ end. The modified ends help protect the RNA from degradation, and the poly (A) tail may facilitate the
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This note was uploaded on 04/01/2012 for the course BIO 141 taught by Professor Dr.cafferty during the Spring '11 term at Emory.

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Chapter_17_From_Gene_to_Protein - Ch. 17: Gene to Protein...

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