Imagine you are carrying out research on the lac operon. You isolate six mutations in the lac operon by measuring the amount of beta-galactosidase made in mutant cell line under three different conditions: no lactose/no glucose; lactose only; and lactose/glucose. Your results are shown in the table. Strain No Lactose, No Glucose Lactose Lactose, Glucose
Wild-type None High Low
Mutant 1 None None None
Mutant 2 None None None
Mutant 3 None Low Low
Mutant 4 None Low Low
Mutant 5 High High Low
Mutant 6 High High Low
You notice that two mutations result in no expression of the lac operon (Mutations 1 and Mutation 2), two mutations result in low expression of the lac operon even in the presence of lactose and the absence of glucose (Mutation 3 and Mutation 4), and two mutations result in constitutive expression of the lac operon (Mutation 5 and Mutation 6).
First, think about what types of mutations could cause the phenotypes you see.
Sort each mutation into the bin that describes its expression pattern.
OF ( opéra tor mutation) lacI (repressor mutation) | lacZ' (beta-galactosidase mutation) (super-repressor) CAP-CAMP binding site mutationmutation in gene for CAP lacP (promoter mutation) No expression Low expression Constitutive expression