MBG 3080 Study Guide - Escherichia Coli, Leucine, Operon

• School: University of Guelph
• Department: Molecular Biology and Genetics
• Course: MBG 3080
• Professor: Lo

Document Summary

Sample questions for mt-1, f/2012: what are nonsense mutations and why are nonsense mutations also polar? (4 marks, what will the final lac phenotype be in the following e. coli mutants. Explain your analysis. (6 marks: a merodiploid carrying a lacis and a laci-d mutation, a double mutant carrying a laci-d and a crp- mutation, a bacteriophage was found to alternately infect two different hosts. It switches between the host specificity at a frequency of approximately 10-4. Describe briefly, two genetic mechanisms that you know can facilitate this switching property. Describe a simple genetic experiment to distinguish between the two mechanisms. (8 marks: the biosynthesis of the amino acid leucine requires the expression of four leuabcd genes arranged in one operon. Located elsewhere is a leur gene which produces a repressor molecule that represses expression of the leuabcd operon. The leur repressor interacts with leucine to form a complex that binds to the leu promoter to repress expression.