Chapter 12 Gene Regulation in Prokaryotes
Part 1
1. The lac repressor is a ___
(1) DNA molecule.
(2) lipid molecule.
(3) carbohydrate.
(4) RNA molecule.
(5) protein molecule.
2. What would be the effect of a mutation in the operator that blocked the lac repressor binding?
(1) The genes would be inducible by lactose.
(2) The lacZYA genes would be expressed constitutively.
(3) The lacZYA genes would not be expressed
(4) The lacZYA genes would be repressed by lactose
(5) None of the above.
3. What would be the effect of a mutation in the lacI gene that blocked binding of the lac repressor to the operator?
(1) The lacZYA genes would be expressed constitutively
(2) The lacZYA genes would be repressed by lactose.
(3) The lacZYA genes would not be expressed.
(4) The genes would be inducible by lactose.
(5) None of the above
4. Which of the following are examples of cis acting genes
(1) LacP, lacO
(2) lacI, lacZ
(3) lacY, lacZ, lacA
(4) lacI, lacY, lacZ
(5) lacI
5. A regulatory site within the leader sequence of the tryptophan operon that controls this operon by diminishing
transcription is called
(1) Transcriptor
(2) Attenuator
(3) Repressor
(4) Operator
(5) upregulator
6. In the absence of tryptophan:
(1) The repressor binds to the co-repressor. Transcription is initiated.
(2) The repressor is inactive and does not bind to the promoter. Transcription is initiated.
(3) The trp operon is repressed and transcription occurs.
(4) The repressor is active and does not bind to the promoter. Transcription does not occur.
7. In the lac and trp operators, the repressor is said to be an allosteric molecule because:
(1) It represses the production of lactose or tryptophan.
(2) It induces the production of lactose or tryptophan.
(3) Interaction with another molecule causes a conformational change in the repressor's active site
(4) It induces the production of lactose or tryptophan.
(5) It diminishes the transcription of the related gene structure.
8. When glucose is present:
(1) cyclic AMP is high, the catabolite activator protein (CAP) binds to the activator binding site, and
transcription of lactose is turned on
(2) cyclic AMP is low, CAP binds to the site activator binding site, and transcription of lactose is turned
on
(3) cyclic AMP is high, CAP does not bind to the activator binding site, and transcription of lactose is
turned on
(4) cyclic AMP is low, CAP does not bind to the activator binding site, and transcription is turned off
9. The lac repressor
(1) binds to the operator and prevents transcription
(2) binds to the CAP site and prevents transcription
(3) binds to the operator and facilitates transcription
(4) binds to the CAP site and facilitates transcription
10. When both glucose and lactose are present
(1) cyclic AMP is high so transcription occurs
(2) the lac repressor binds with the lactose and transcription occurs
(3) RNA polymerase is able to bind to the operator so transcription occurs
(4) transcription is turned off
11. The operator is
(1) another name for the terminator of a gene (2) a DNA site bound by repressor proteins
(3) a protein that coordinates gene expression
12. ___binds to the repressor and turn on the transcription of the structural genes in the Lac operon.
(1) cAMP
(2) lactose
(3) allolactose
(4) CRP
13. If a normal (wild type) repressor is added in vitro, which DNA fails to bind the repressor?
(1) I+ O+ Z+
(2) I+ Oc Z+
(3) I+O+ Z+
(4) I+ O+ Z-
(5) All of the above will bind the repressor
Part 2 Ture or false
1. In the absence of glucose, when lactose is present it combines with the repressor, allowing RNA polymerase to
carry on transcription. ( )
2. When both glucose and lactose are absent, transcription occurs.( )
Part 3 question
How does an extracellular signal control its target gene expression by modulating the activity of a
transcriptional regulator?
What are the general principles of transcription of regulation in both prokaryotic and eukaryotic
cells?
A bacterium is found to metabolize a rare sugar produced by a plant that the bacteria grow on.
However, the bacteria prefer glucose as the energy source. The problem is, if you want to finish this course
with a satisfied score, you must figure out the regulatory mechanism that the bacteria used to determine the
sugar choice.
