Questions on Prokaryotic Gene Regulation
Multiple Choice Questions: Prokaryotic Gene Regulation
1. What is the primary method of gene regulation in prokaryotes?
A) DNA replication
B) Alternative splicing
C) Operon system
D) Histone modification
E) mRNA capping
2. What is an operon?
A) A single protein-coding gene
B) A sequence of DNA that initiates translation
C) A cluster of genes under the control of a single promoter
D) A region of DNA that codes for tRNA
E) A ribosomal RNA processing unit
3. Which operon is responsible for lactose metabolism in E. coli?
A) Trp operon
B) Lac operon
C) Ara operon
D) His operon
E) Gal operon
4. What is the function of the promoter in an operon?
A) Binds the repressor
B) Codes for enzymes
C) Signals RNA polymerase to begin transcription
D) Terminates translation
E) Binds ribosomes
5. Which protein binds to the operator to block transcription in the lac operon?
A) RNA polymerase
B) Activator
C) Repressor
D) Enhancer
E) Regulator
6. What molecule acts as an inducer in the lac operon?
A) Glucose
B) Allolactose
C) Galactose
D) ATP
E) Fructose
7. What happens when the lac repressor binds to the operator?
A) RNA polymerase initiates transcription
B) Translation is enhanced
C) Transcription is blocked
D) Lactose is broken down
E) Genes are duplicated
8. Which condition leads to full activation of the lac operon?
A) Presence of glucose
B) Absence of lactose
C) Presence of both glucose and lactose
D) Presence of lactose and absence of glucose
E) Presence of galactose
9. What is the role of CAP (catabolite activator protein) in the lac operon?
A) Repress transcription
B) Degrade mRNA
C) Facilitate RNA polymerase binding
D) Inhibit translation
E) Bind to ribosomes
10. What increases the binding of CAP to the promoter?
A) Glucose
B) ATP
C) cAMP
D) Lactose
E) NADH
11. What is the effect of high glucose on the lac operon?
A) Stimulates transcription
B) Prevents lactose binding
C) Increases cAMP levels
D) Reduces cAMP levels
E) Enhances CAP binding
12. The trp operon is an example of what type of operon?
A) Inducible
B) Repressible
C) Constitutive
D) Translational
E) Structural
13. What happens to the trp operon in the presence of tryptophan?
A) It is fully activated
B) Repressor binds to the operator
C) cAMP levels increase
D) Transcription increases
E) Ribosomes degrade
14. Which gene in the lac operon codes for β-galactosidase?
A) lacY
B) lacZ
C) lacA
D) lacI
E) trpE
15. What type of feedback regulation does the trp operon use?
A) Positive feedback
B) Feedback inhibition
C) Signal transduction
D) Genetic mutation
E) RNA silencing
16. Which component is NOT typically part of an operon?
A) Promoter
B) Operator
C) Coding genes
D) Enhancer
E) Regulatory gene
17. What binds to the operator in a repressible operon like trp?
A) RNA polymerase
B) Corepressor-repressor complex
C) CAP
D) cAMP
E) Ribosome
18. Which of the following is true about repressible operons?
A) Usually off, turned on by inducers
B) Always off
C) Usually on, turned off by repressors
D) Regulate tRNA production
E) Used only in eukaryotes
19. The lacI gene in the lac operon encodes for:
A) Lactase
B) Permease
C) Repressor protein
D) RNA polymerase
E) Glucose transporter
20. What kind of control is exhibited by the lac operon when glucose is present?
A) Positive control
B) Negative control
C) Feedback inhibition
D) Co-translational control
E) RNA interference
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Answer Key:
1. C
2. C
3. B
4. C
5. C
6. B
7. C
8. D
9. C
10. C
11. D
12. B
13. B
14. B
15. B
16. D
17. B
18. C
19. C
20. B
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