Lecture 10 Prok Trxn Global Control

Lecture 10 Prok Trxn Global Control - P ROKARYOTIC T...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
PROKARYOTIC TRANSCRIPTION Fine control of genes Pt 2, and Global Regulation 1 Wednesday, September 28, 2011
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
LAST TIME The three stages of transcription in prokaryotes Regulation of small groups of coordinately regulated genes (operon) The Lac Operon Mechanism of repression by LacI Two Models Experimental evidence for Model 1 2 Wednesday, September 28, 2011
Background image of page 2
GLOBAL REGULATION How does LacI repress the Lac Operon: Experiment 2 and model Global regulation in bacteria Examples in sporulation, heat shock, quorum sensing, and circadian rhythms 3 Wednesday, September 28, 2011
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Learning Outcomes 1. Describe the LacI experiment that supports Model 2. 2. Present a model for lacI repression that resolves the apparent contradiction between the two experimental results presented ( covers Lecture 8 and 9) 3. Describe, in general terms, how suites (or collections) of genes can be regulated at the same time in prokaryotic cells 4. Describe speciFc examples of global regulation. 5. Discuss and apply the experimental design illustrating that cyanobacteria is under circadian control By the end of this lecture, you should be able to: 4 Wednesday, September 28, 2011
Background image of page 4
From last time: Is this model experimentally verifed? 5 Wednesday, September 28, 2011
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
MECHANISM OF REPRESSION OF THE LAC OPERON BY LACI Model 1: Lac repressor (lacI) binds Operator Suggests that RNAP can still bind Promoter, but only makes short (~6nt) RNAs Stuck in initiation phase, no elongation phase 6 Wednesday, September 28, 2011
Background image of page 6
Lac repressor ( lacI ) binds Operator This physically blocks polymerase from binding to the promoter. No initiation phase can take place. Model 2 MECHANISM OF REPRESSION OF THE LAC OPERON BY LACI 7 Wednesday, September 28, 2011
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Fig. 7.8 Lane 1 No Lac Repressor No IPTG* Lane 2 Lac Repressor No IPTG Lane 3 Lac Repressor IPTG * IPTG = mimic of allolactose, more stable caveat: ABNORMALLY HIGH amounts of RNAP used Conclusion: Repressor does not block RNAP from binding DNA 8 Wednesday, September 28, 2011
Background image of page 8
Lac repressor ( lacI ) binds Operator This physically blocks polymerase from binding to the promoter (i.e. RNAP will not bind promoter in presence of LacI). No initiation phase can take place. Model 2 MECHANISM OF REPRESSION OF THE LAC OPERON BY LACI 9 Wednesday, September 28, 2011
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lac repressor ( lacI ) binds Operator This physically blocks RNAP from binding to the promoter. If we assume : RNAP-promoter complex is in equilibrium with free RNAP, repressor prevents reattachment IF so , adding Heparin will mimic adding repressor (i.e. both will prevent RNAP from reattaching to DNA) Model 2 MECHANISM OF REPRESSION OF THE LAC OPERON BY LACI 10 Wednesday, September 28, 2011
Background image of page 10
Fig. 7.9 What is the effect of lac repressor on dissociation of RNAP from the promoter? Experiment:
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 52

Lecture 10 Prok Trxn Global Control - P ROKARYOTIC T...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online