Question

Regulation of Gene Expression Question. Help with regulatory proteins (operators) and protein binding sites!!

1. In studying the bacterial the srp operon, you have isolated two different mutants (con1 and con2) that cause constitutive expression of the srp operon (constitutive expression of srp1 and srp2). One of the mutants has a mutation in a DNA binding site (e.g. operator), and the other has a loss-of-function mutation in the gene that encodes a protein that binds to the DNA binding site (e.g. repressor protein).

You perform an analysis using partial diploids to determine which of the two mutants has a defect in the binding site and which of the two mutants has a mutation in the gene encoding the binding protein.

a. Assuming you can assay levels of the two Srp proteins, what results do you predict for the two strains (i and ii below) if con2 encodes the regulatory protein and con1 is the regulatory binding site? In predicting results, indicate whether expression of the Srp1 and Srp 2 proteins will be constitutive or inducible (you will circle an answer in the bolded region below). 2 pts

i. (a) con1^-con2⁺srp1^-srp2⁺/ (b) con1⁺con2⁺srp1⁺srp2^-

ii. (a) con1⁺con2^-srp1^-srp2⁺/ (b) con1⁺con2⁺srp1⁺srp2^-

b. What results do you predict for the two strains (i and ii) if con1 encodes the regulatory protein and con2 is the regulatory binding site? 2 pts

Answer for a(i) (circle either constitutive or inducible for each gene):

srp1 constitutive / inducible

srp2 constitutive / inducible

Answer for a(ii) (circle either constitutive or inducible for each gene):

srp1 constitutive / inducible

srp2 constitutive / inducible

Answer for b(i) (circle either constitutive or inducible for each gene):

srp1 constitutive / inducible

srp2 constitutive / inducible

Answer for b(ii) (circle either constitutive or inducible for each gene):

srp1 constitutive / inducible

srp2 constitutive / inducible