Control of Gene Expression

   I. Overview
      A. Cell types
         1. housekeeping proteins
      B. External signals
      C. Control steps
      D. Constitutive expression

  II. Transcriptional Switches
      A. Background
         1. regulatory DNA sequences
         2. transcription regulators
            a. DNA-binding motifs
            b. dimerization
      B. Repression
         1. Tryptophan operon
            a. operator
            b. tryptophan repressor
      C. Activators
      D. Lac operon
         1. genes & enzymes
            a. beta-galactosidase - _lacZ_
            b. galactoside permease - _lac Y_
            c. galactoside acetyltransferase - _lacA_
         2. negative control
            a. _lac_ repressor
               a) allolactose
            b. leaky
         3. positive control
            a. cyclic-AMP
            b. catabolite activator protein
               1) activator-binding site
      E. Sigma factor switches
         1. heat shock proteins
      F. Eukaryotic regulators
            a. enhancers
         1. loop
         2. mediator
         3. euk. repressors

 III. Cell type control
      A. one gene - many regulators
         1. combinatorial control
      B. one regulator - many genes
      C. Cell types
         1. ex. MyoD
      D. Daughter cell transmission
         1. epigenetic inheritance
         2. positive feedback loop
         3. chromatin structure
            a. heterochromatin
            b. euchromatin
         4. DNA methylation
            a. methyltransferase

  IV. Post-transcriptional Controls
      A. Alternate splicing
      B. Riboswitches
      C. Untranslated regions of mRNA
         1. 5'
         2. 3'