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ippose Jim isolated four E. coli mutants, mut1 to mut4, that showed abnormal exp

ID: 259778 • Letter: I

Question

ippose Jim isolated four E. coli mutants, mut1 to mut4, that showed abnormal expression of the lac ease protein. To identify the defect in each mutant, he determined the relative levels of lac permease or the laC protein in each mutant. He also generated F' plasmids that contained the wild type (wt) lac o operon from each of the four mutants. He determined lac permease protein levels in partial diploids of wild type cells containing F' lac from each mutant and mutant cells containing wild type F' lac. All measurements were carried out in cultures grown in the presence (+) or the absence () of lactose and glucose, as shown in the table in cell genotype F' plasmid genotype format. E. coli strain lactoselactoselactose lactose - glucose +glucoseglucose+glucose 100 100 100 100 100 100 100 0 mut1 mut1 F' lac from wt 100 wt /F' lac from mut1 0 100 100 mut2 F' lac from wt 100 wtF' lac from mut2100 mut3 mut3 F' lac from wt 0 wt / F' lac from mut3 mut4 mut4 F' lac from wt 0 0 0 0 100 Continued below.

Explanation / Answer

Mutant 1 = Deletion of the repressor gene

Mutant 2 = Deletion of operator

Mutant 3 = Defective Promoter

Mutant 4 = Defective CAP - binding site