Gene Regulation DNA Replication Glucose

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					     Bio 221 Discussion # 5 – Prokaryotic Gene Regulation & DNA Replication



I. Operons -- Review Questions & Animated Views

Repressors & Operators
       1) Which of these (repressor/operator) is a protein?

       2) Which of these (repressor/operator) is the DNA region to which the protein
       binds?

       3) How do the repressor & operator recognize (bind to) each other?

       4) What is the effect of repressor binding on RNA polymerase's ability to bind &
       carry out transcription?

           ** See Animation**

       5) Under what conditions does Trp repressor bind DNA?

       6) Under what conditions does Lac repressor bind DNA?

       7) Do these responses to Trp & Lac make good energetic sense?


cAMP-CAP as an Example of an Activator
     1) What molecule binds to CAP, and enables CAP to bind DNA?

       2) What is the relationship between glucose levels and cAMP concentration?

       3) Given your answers to the prior 2 questions, what is the relationship between
       glucose levels and the ability of CAP to bind DNA?

               ** See Animation and Figure**


II. Operon practice problems

The attached page contains several examples of mutations in the various DNA sequences
involved in lac operon function. In some cases, bacteria can be made to be “partial
diploids” (merodiploids), that is, contain two alleles for a given sequence. Those situations
are indicated by a slash separating the different version of those sequences.

After we discuss a few examples as a class, each group should work on two or three of the
problems on the attached lac operon worksheet, as assigned by your instructor. After
discussing them, you’ll work with your group to complete the five problems on the final
sheet, and turn in this completed sheet at the end of class, one per group.
Bio 221        Discussion # 5                     lac operon worksheet
Explain how each operon is regulated and indicate what, if any, enzyme is made.
       Symbols: I = regulator gene; P = promoter; O = operator; Z = beta-galactosidase gene
       Superscript Symbols: + = normal allele; - = mutant (non-functional) allele; s = "super" allele (product can't be inactivated)


                                                           Functional Nonfunctional   No
                                                            Enzyme      Enzyme      Enzyme
                 Genotype           Medium contains:         Made        Made        Made                       Explanation
                  + + + +
                 I P O Z         No Lactose No Glucose
                  + + + +
                 I P O Z         No Lactose  Glucose
 Ex. 1            + + + +
                 I P O Z          Lactose   No Glucose
                  + + + +
                 I P O Z          Lactose    Glucose
                  + + - +
                 I P O Z         No Lactose No Glucose
                  + + - +
                 I P O Z         No Lactose  Glucose
 Ex. 2            + + - +
                 I P O Z          Lactose   No Glucose
                  + + - +
                 I P O Z          Lactose    Glucose
             + + - +    + + +
            I P O Z /P O Z       No Lactose No Glucose
             + + - +    + + +
            I P O Z /P O Z       No Lactose  Glucose
 Ex. 3       + + - +    + + +
            I P O Z /P O Z        Lactose   No Glucose
             + + - +    + + +
            I P O Z /P O Z        Lactose    Glucose
                  - +  + +
                 IP O Z          No Lactose No Glucose
                  - + + +
                 IP O Z          No Lactose  Glucose
   4              - + +  +
                 IP O Z           Lactose   No Glucose
                  - + + +
                 IP O Z           Lactose    Glucose
                - + + +    +
               I P O Z /I        No Lactose No Glucose
                - + + +    +
               I P O Z /I        No Lactose  Glucose
   5            - + + +    +
               I P O Z /I         Lactose   No Glucose
                - + + +    +
               I P O Z /I         Lactose    Glucose
                  s + + +
                 I P O Z         No Lactose No Glucose
                  s + + +
                 I P O Z         No Lactose  Glucose
   6              s + + +
                 I P O Z          Lactose   No Glucose
                  s + + +
                 I P O Z          Lactose    Glucose
                s + + +    +
               I P O Z /I        No Lactose No Glucose
                s + + +    +
               I P O Z /I        No Lactose  Glucose
   7            s + + +    +
               I P O Z /I         Lactose   No Glucose
                s + + +    +
               I P O Z /I         Lactose    Glucose
                  + + + -
                 I P O Z         No Lactose No Glucose
                  + + + -
                 I P O Z         No Lactose  Glucose
   8              + + + -
                 I P O Z          Lactose   No Glucose
                  + + + -
                 I P O Z          Lactose    Glucose
Names_________________________________________________________________________________________                                                  Section:_______

Pledges___________________________________________________________________________________________


Bio 221 Discussion 5:                                               lac operon worksheet Assignment

Work the following problems with your group, and turn in one group copy at the end of class.                                    (5 points)

Explain how each operon is regulated and indicate what, if any, enzyme is made.
      Symbols: I = regulator gene; P = promoter; O = operator; Z = beta-galactosidase gene
      Superscript Symbols: + = normal allele; - = mutant (non-functional) allele; s = "super" allele (product can't be inactivated)

                                                                                              Functional Nonfunctional   No
                                                                                               Enzyme      Enzyme      Enzyme
                    Genotype                                           Medium contains:         Made        Made        Made                 Explanation
                    +           -           +       +
                    I PO Z                                          No Lactose   No Glucose
                    +           -           +       +
                    I PO Z                                          No Lactose    Glucose
                    +           -           +       +
  9                 I PO Z                                           Lactose     No Glucose
                    +           -           +       +
                    I PO Z                                           Lactose      Glucose
                +       +           -       +           +
            I P O Z /O                                              No Lactose   No Glucose
                +       +           -       +           +
            I P O Z /O                                              No Lactose    Glucose
                +       +           -       +           +
 10         I P O Z /O                                               Lactose     No Glucose
                +       +           -       +           +
            I P O Z /O                                               Lactose      Glucose
            +       -       -           +           +       +
            I P O Z /P O                                            No Lactose   No Glucose
            +       -       -           +           +       +
            I P O Z /P O                                            No Lactose    Glucose
            +       -       -           +           +       +
 11         I P O Z /P O                                             Lactose     No Glucose
            +       -       -           +           +       +
            I P O Z /P O                                             Lactose      Glucose
        -   +       +       +               +       -   +       +
       I P O Z /I P O Z                                             No Lactose   No Glucose
        -   +       +       +               +       -   +       +
       I P O Z /I P O Z                                             No Lactose    Glucose
        -   +       +       +               +       -   +       +
 12    I P O Z /I P O Z                                              Lactose     No Glucose
        -   +       +       +               +       -   +       +
       I P O Z /I P O Z                                              Lactose      Glucose
                +       +           +           +       S
            I P O Z /I                                              No Lactose   No Glucose
                +       +           +           +       S
            I P O Z /I                                              No Lactose    Glucose
                +       +           +           +       S
 13         I P O Z /I                                               Lactose     No Glucose
                +       +           +           +       S
            I P O Z /I                                               Lactose      Glucose

				
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