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Unformatted text preview: used for counterselection, the number of h+ tet-r colonies is 1000-fold lower than the number of h+ str-r colonies found when streptomycin sensitivity is used for counterselection. Suggest an explanation for the difference. 3. You find a mutant strain of E. coli that produces betagalactosidase and permease constitutively. List the two mutations that could cause this phenotype. 4. Given the two mutations you listed in #3, what experiment could you use to distinguish between them? Explain how you would know which mutation was which (i.e., predict the outcome of your experiment for each mutation). Be brief (bullet points are fine)....
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- Fall '08