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Average = 79

Average = 79. Average = 85. Kavanagh et al discussion moved up to next Tuesday - Allows for last class to be a review session. Goals Lac operon Eukaryotic enhancers Transcription factors Signal integration. The lac operon promoter.

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Average = 79

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  1. Average = 79 Average = 85

  2. Kavanagh et al discussion moved up to next Tuesday - Allows for last class to be a review session

  3. Goals • Lac operon • Eukaryotic enhancers • Transcription factors • Signal integration

  4. The lac operon promoter LacZ - BetaGalactosidase - cleaves lactose into usable subunits LacY - Lactose permease - transports lactose across the cell membrane LacA - Eliminates toxic molecules that are co-transported Operator - Binds repressors CAP site - binds cap proteins (activator)

  5. The activator and repressor are both inhibited by sugars

  6. Physical interactions regulate lac operon transcription

  7. Cap recruits Polymerase via interaction with the CTD of the alpha subunit

  8. The cap activator is a helix-turn-helix motif • Bind DNA as a dimer • Requires two similar sequences of DNA in reverse order

  9. Lac repressor forms a tetramer between two operator sites (primary and secondary)

  10. Discovery of the cis-trans model of gene regulation Repressor acting in trans

  11. Operator (repressor binding site) operates in cis

  12. Regulation in eukaryotes follows the same principles as prokaryotes, but involves more regulatory sequences - *Can regulate access to DNA via nucleosomes

  13. Transcriptional regulators (tx factors) are modular - Experimental loss of n-terminal end of activator - Experimental fusion of n-terminal domian of an activator to c terminal of a repressor

  14. Common DNA binding motifs Homeodomain DNA recognition Zinc finger domain Helix turn helix domain

  15. Eukaryotic activators don’t often interact directly with RNA polymerase Interaction with histones Interaction with the mediator complex

  16. Regulatory elements can be kilobases away, or on different chromosomes

  17. Signal integration

  18. Theoretical mechanisms of repression

  19. Example of signal transduction - Extracellular signaling molecule (ie SHH) initiates a cascade that alters transcription

  20. Lac operon integrates signals from outside the cell

  21. Kavanagh et al discussion moved up to next Tuesday - Allows for last class to be a review session

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