Week 2 Handout - bacteria without answers

Week 2 Handout - bacteria without answers - Discussion...

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Discussion Problems (Lac Operon) Week 7 Question 1 Learning objectives: 1) Understand the rationale and strategies behind a genetic screen. 2) Predict the types of mutations that might be expected in a genetic screen. 3) Be able to predict trans or cis activity of regulators using merodiploids. When studying the lac operon researchers did two different mutant screens to identify important factors that regulate of the lac operon. These screens were done in the presence of the chemical X-Gal, a substrate for the LacZ enzyme. LacZ can metabolize X-Gal from a colorless compound to a blue compound. Screen 1: Mutants with constitutive expression of LacZ (constitutive means "always on", even when no lactose is present). A) Conditions for screen: B) Classes of mutant: Two classes of mutant can result in blue colonies that are due to constitutive expression of the lac operon. Screen 2: Mutants with no expression in presence of lactose. C) Conditions for screen: D) Classes of mutant:
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Predictions based on the cis / trans hypothesis of gene regulation. The bacterial mutants (either I-O+Z+ or I+O C Z+) are complemented with a wild type version of the F' plasmid. In this case to become merodiploid for only the I or O locus respectively;
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This note was uploaded on 07/17/2011 for the course BIO 151 taught by Professor Grinblat during the Summer '08 term at University of Wisconsin.

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Week 2 Handout - bacteria without answers - Discussion...

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