Biochemistry Questions and Answers – Regulation of Gene Expression in Prokaryotes-1

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This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Regulation of Gene Expression in Prokaryotes-1”.

1. Which of the following statements is not correct?
a) Bacteria possess only one type of RNA polymerase
b) Attenuation is a regulatory process used by bacteria to control the initiation of transcription
c) Repressor binds to operator
d) Bacterial genes are polycistronic
View Answer

Answer: b
Explanation: Attenuation results in premature termination of transcription.
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2. Which of the following bacterial operon is not controlled by attenuation?
a) Arabinose
b) Tryptophan
c) Leucine
d) Histidine
View Answer

Answer: a
Explanation: Arabinose is a carbohydrate.

3. Which of the following is the most appropriate definition of an operator?
a) A non-coding, regulatory DNA sequence that is bound by RNA polymerase
b) A non-coding, regulatory DNA sequence that is bound by a repressor protein
c) A DNA-binding protein that regulates gene expression
d) A cluster of genes that are regulated by a single promoter
View Answer

Answer: b
Explanation: A repressor binds to the operator.
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4. To which class of transcription factor do nuclear receptors belong?
a) Zinc finger proteins
b) Leucine zipper proteins
c) Helix-turn-helix proteins
d) Helix-loop-helix proteins
View Answer

Answer: a
Explanation: Nuclear receptors belong to the zinc finger motif.

5. Which of the following statements about lac operon in e.coli is true?
a) Promoter is the binding site for the lac repressor
b) Operon is only switched on in the absence of lactose in the growth medium
c) β-galactosidase is only produced in large quantities when the lac repressor is bound to the operator
d) Lac operon mRNA is a polycistronic mRNA
View Answer

Answer: d
Explanation: Bacterial genes are polycistronic and genes in eukaryotes are monocistronic.
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6. Which of the following statements regarding the regulation of trp operon expression by attenuation is correct?
a) Rapid translation of the leader peptide prevents completion of mRNA transcript
b) Rapid translation of the leader peptide allows completion of mRNA transcript
c) The leader peptide sequence encodes enzymes required for tryptophan synthesis
d) The leader peptide sequence contains no tryptophan residues
View Answer

Answer: a
Explanation: Attenuation results in premature termination of transcription.

7. Which of the following increases gene expression as much as 200-fold?
a) TATA box
b) Insulator
c) Enhancer
d) CAAT box
View Answer

Answer: c
Explanation: Only enhancers can increase gene expression as much as 200-fold.
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8. The mechanism by which CBP activates transcription is?
a) CBP has DNA methyl transferase activity
b) CBP has histone acetyl transferase activity
c) CBP interacts with the basal transcription complex
d) CBP interacts with the basal transcription complex and has histone acetyl transferase activity
View Answer

Answer: c
Explanation: CBP interacts with the basal transcription complex and activates transcription.

9. RNAi stands for ____________
a) RNA inducer
b) RNA interference
c) RNA intron
d) RNA insertion
View Answer

Answer: b
Explanation: RNAi stands for RNA interference.
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10. Which of the following about mRNA stability is not correct?
a) Regulation of mRNA stability is a way of regulating gene expression
b) Prokaryotic mRNAs have a half-life of only a few minutes
c) Histone mRNAs have especially long poly-A tails and are stable
d) It is thought that poly-A tails stabilize eukaryotic mRNAs
View Answer

Answer: c
Explanation: Histone mRNAs lack poly-A tails so they are unstable.

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