Download 2011_OperonQuiz - MrsPalffysAPBio2013

AP Biology – Inselberger
Operon Quiz Partner—no notes
NAME: ______________________________
Answer the 8 multiple-choice questions using the picture above. Recall that mutations typically disable a
gene & prevent gene expression. Predict the phenotype of the gene mutants in the questions below.
All questions come from the following website:
http://www.phschool.com/science/biology_place/biocoach/lacoperon/quiz.html
Enter the responses you (and your partner) generated in class and check your answers online after class. A
nifty animation of the operon is provided if you correctly answer each question!
1. Predict the phenotype of a lacI mutant.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
2. If a second wild type or normal copy of the lacI gene (just lacI and not lacZ, lacY, or lacA) is
introduced into the lacI mutant cell, what would be the phenotype of this partial diploid (also referred
to as a merodiploid)?
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
3. Predict the phenotype of a lacI S or "super-repressor" mutant. A lacI S mutant synthesizes a repressor
that cannot bind to the inducer.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
4. Predict how a lacI S mutant (as defined previously in question #3) would be affected by the
construction of a merodiploid that has a second normal copy of the lacI gene.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
5. Predict the phenotype of an operator mutant (O c) that would prevent the binding of the repressor.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
6. Predict the phenotype of a promoter mutant (lacP) that has a mutation in the promoter for the lac
operon.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently only in the presence of lactose.
c. The lac genes would be expressed continuously.
d. The lac genes would never be expressed efficiently.
7. Predict the phenotype of a lacZ mutant, which has a mutation in the gene for β-galactosidase.
a. The production of all protein products would be affected.
b. The production of β-galactosidase would be affected, but other protein products would be
unaffected.
c. The production of β-galactosidase would be affected, and the production of some other protein
products might also be affected.
d. The production of β-galactosidase would be unaffected, but other protein products would be
affected.
8. Predict the phenotype of a lacY mutant, which has a mutation in the gene for lactose permease.
a. The lac genes would be expressed efficiently only in the absence of lactose.
b. The lac genes would be expressed efficiently until the lactose supply in the cell is exhausted.
c. The lac genes would be expressed continuously.
d. Expression of the lac genes would cease immediately.
For more operon mini animations and self-check quiz questions, go to:
http://nhscience.lonestar.edu/biol/operon/opfram1.html
Use the remaining class time wisely!