Question

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

Part A

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 reset help

Answer 1

No expression Low expression Constitutive expression lacP (promoter mutation) mutation in gene for CAP lacI (repressor mutation) lacZ (beta-galactosidase mutation) CAP-CAMP binding site mutation OF (operator mutation) (super-repressor)