Lecture 6 Part 2 (lec 7)

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25 Mar 2012
Lecture 7 Feb. 9/12
Transcription (I, prokaryotic)
RNA overview
Encode proteins, mRNA
Functions as rRNA and tRNA, most RNA are in these forms
One Gene can code many RNA sequences
Transcription process controls:
1) Abundance of RNA produced
2) Timing of protein synthesis
3) Location of creating the proteins
RNA polymerase (General)
Enzyme that catalyzes creation of RNA
Unlike DNA polymerase, does not require a primer
Also contains a 3’-5’ exonuclease correction enzyme
1) Separates a DNA double helix
2) Uses a single stranded DNA (ssDNA) as a template for RNA, RNA/DNA hybrid is
temporarily created
3) Transcription of RNA strand occurs in 5’-3’ direction
4) Uptakes ribonucleoside triphosphates (rNTPs)
5) Hydrolysis of the rNTPs provides energy and corresponding base pairs
Transcription cycle (prokaryotic)
Promoter: Nucleotide sequence RNA polymerase binds to before transcription
Sigma factor: Enables RNA polymerase complex to bind to a promoter to signal
transcription, selective based on type of gene
Sigma factor + core RNA polymerase = RNA polymerase holoenzyme
Holoenzyme determines if transcription is upstream or downstream from promoter
Enhancer + NtrC: “kisses” RNA polymerase, helps increase speed of transcription
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