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PRINT - transcription_notes from 11-30

PRINT - transcription_notes from 11-30 - Skeleton 5 notes...

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Skeleton 5 notes Hogan, Chem 130 Lecture notes Transcription I. Introduction A. Transcription is the process of synthesizing a RNA polymer from individual NTPs in a DNA directed manner. B. The transfer of the genetic information encoded in DNA through the intermediate molecule, RNA, must occur with great fidelity. Life cannot support unfaithful interpretation of the genetic information. II. The mechanics of transcription are conserved throughout the evolution; however, differences RNA synthesis do exist between prokaryotes and eukaryotes. A. Transcription in prokaryotes 1. Prokaryotes: no organized nucleus Txn and translation occur in cytoplasm. One RNApol synthesizes all of cell’s RNA except short RNA primers for DNA replication 2. dsDNA ssRNA Protein B. Transcription in eukaryotes 1. Eukaryotes: distinct nucleus 2. Txn. in nucleus, translation (protein synthesis) in cytoplasm—the two rxns. are compartmentalized 3. Eukaryotic mRNA (messenger RNA) is processed prior to translation. Not as simple as dsDNA—ssRNA--Protein III. Types of RNA in cells A. rRNA (ribosomal RNA): integral structural component of the ribosome. Makes up ~66% of the ribosome mass B. mRNA (messenger RNA): Sequence that directs protein synthesis C. tRNA (transfer RNA): structurally compact RNAs that deliver amino acids to the ribosome during translation Note: RNA does not contain thymine. RNA contains uracil. –OH on 2’ carbon of ribose sugar. 1
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Skeleton 5 notes Hogan, Chem 130 Lecture notes Prokaryotic transcription D. Enzyme: RNA polymerase (RNAP) E. Structure of RNAP 1. Large, multisubunit enzyme (m.w. ~500,000) 2. Core enzyme ( αββ ϖ ) 3. Holo enzyme ( αββ ϖσ ) – contains the “sigma factor” 4. Enzyme requires Mg 2+ F. Transcription requires a DNA template 1. Unlike DNA polymerase, only 1 strand is required as a “template” NONCODING STRAND Also not all regions of DNA template are transcribed 2. RNA synthesis proceeds in the 5’ 3’ direction CODING STRAND HAS SAME INFO AS DNA EXCEPT U INSTEAD OF T Overall reaction: (RNA) n + NTP (RNA) n+1 + PP i Followed by hydrolysis of PP i IV.
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