Genetics Homework Chapter 16 Graded Questions 1

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Genetics Homework Chapter 16 Graded Questions 1. What is the difference between positive and negative control? What is the difference between inducible and repressible operons? 2. Briefly describe the lac operon and how it controls the metabolism of lactose. 3. What is catabolite repression? How does it allow a bacterial cell to use glucose in preference to other sugars? 4. For each of the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor, inactive repressor, active activator, or inactive activator. a. Negative control in a repressible operon b. Positive control in a repressible operon c. Negative control in an inducible operon d. Positive control in an inducible operon 5. For E. coli strains with the lac genotypes shown below, use a plus sign (+) to indicate the synthesis of B-galactosidase and permease and a minus sign (-) to indicate no synthesis of the proteins. Lactose absent Lactose present Genotype B-galactosidase Permease B-galactosidase Permease of Strain lacI+ lacP+ lacO+ lacZ+ lacY+ lacI- lacP+ lacO+ lacZ+ lacY+ lacI+ lacP+ lacOC lacZ+ lacY+ lacI- lacP+ lacO+ lacZ+ lacY- lacI- lacP- lacO+ lacZ+ lacY+