Download Lac Operon - Iowa State University

Prokaryotic Gene Regulation II
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Lilli Howard
BIOL/GEN 313
Dr. Vollbrecht
04/02/14
1. Which mode of regulation is shown in the lac operon:
a. In the presence of lactose
b. In the absence of glucose
2. LacZ, lacY and lacA are ___________________ genes of the operon.
a. Their products function to __________________________________________
3. LacO and lacP are _____________________________________ of the operon.
a. LacO binds ________________________________________________
b. LacP binds _________________________________________________
4. Describe the function of the lac operon:
a. under normal conditions
b. In the presence of lactose
c. In the absence of lactose
d. Low levels of glucose
5. What is the function of lacI? What does it mean that it acts in trans?
6. What is the function of lacO and what does it mean that it acts in cis?
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu
7. What is the function of allolactose in regulation of the lac operon?
a) inducer
b) repressor
c) activator
d) promoter
e) regulatory protein
8. What is the function of cAMP in regulation of the lac operon?
a) it activates a repressor protein
b) it activates an activator protein
c) it inactivates a repressor protein
d) it inactivates an activator protein
9. 14. A mutant E. coli strain, grown under conditions that normally induce the lac operon,
produces high amounts of ß-galactosidase. What is a possible genotype of the cells?
a) lacI+ lacP+ lacO+ lacZ- lacY+ lacA+
b) lacI+ lacP+ lacOc lacZ+ lacY+ lacA+
c) lacI- lacP+ lacO+ lacZ- lacY+ lacA+
d) lacI+ lacP- lacO+ lacZ+ lacY+ lacA+
10. A mutant E. coli strain, grown under conditions that normally induce the lac operon, does
not produce ß-galactosidase. What is a possible genotype of the cells?
a) lacI+ lacP+ lacO+ lacZ+ lacY- lacA+
b) lacI+ lacP+ lacOc lacZ+ lacY+ lacA+
c) lacI+ lacP+ lacO+ lacZ+ lacY+ lacA+
d) lacI+ lacP- lacO+ lacZ+ lacY+ lacA+
11. What is the role of the lacZ gene product, the enzyme ß-galactosidase?
a) ß-galactosidase facilitates the entry of lactose into the bacterial cell
b) ß-galactosidase removes the toxic by-products of lactose digestion from the bacterial
cell
c) ß-galactosidase converts lactose to glucose and galactose
d) ß-galactosidase converts simple sugars to lactose
12. Which molecule is the true inducer of the lac operon?
a) dextrose
b) glucose
c) allolactose
d) galactose
13. What would be the effect of a mutation in the lacI gene that prevented the repressor from
binding to lactose?
a) lacZ, lacY, and lacA would not be transcribed
b) lacZ, lacY, and lacA would be induced by lactose
c) lacZ, lacY, and lacA would be repressed by lactose
d) lacZ, lacY, and lacA would be expressed constitutively
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu