Question 1

Which of the following best describes the role of attenuation in the regulation of the trp operon in *E. coli*?

Accepted Answer

Attenuation causes premature termination of transcription in response to high tryptophan levels.

Question 2

A mutation in the leader region of the trp operon removes both tryptophan codons. What is the most likely effect on attenuation?

Accepted Answer

Attenuation will occur regardless of tryptophan levels.

Question 3

Which of the following is a key difference between gene regulation in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes often regulate gene expression at multiple levels, including chromatin modification and mRNA processing.

Question 4

Which enzyme is responsible for adding acetyl groups to histone proteins, and what is the effect on gene expression?

Accepted Answer

Histone acetyltransferase (HAT); increases gene expression

Question 5

In the context of the trp operon, what is the function of tryptophan when it is abundant in the cell?

Accepted Answer

It acts as a corepressor, activating the repressor protein to bind the operator and block transcription.

Question 6

Which of the following statements about eukaryotic gene expression is TRUE?

Accepted Answer

Each structural gene has its own promoter and is transcribed separately.

Question 7

A researcher observes that a mutant fly has histones resistant to acetylation. What phenotype would you expect?

Accepted Answer

Decreased levels of gene expression

Question 8

Which of the following is NOT a function of the C-terminal domain (CTD) of RNA polymerase II in eukaryotes?

Accepted Answer

Direct binding to the TATA box

Question 9

Which of the following best explains why attenuation does NOT occur in eukaryotes?

Accepted Answer

Transcription and translation are separated in time and space in eukaryotes.

Question 10

Which of the following modifications is most likely to be observed in euchromatin and is associated with active gene expression?

Accepted Answer

Histone 4 lysine 27 acetylation

Question 11

Which of the following is a direct effect of histone acetylation?

Accepted Answer

Neutralization of positive charge on lysine residues, resulting in relaxed chromatin and increased transcription

Question 12

Which of the following is TRUE regarding the regulation of flowering time in Arabidopsis by histone modification?

Accepted Answer

Active FLD gene reduces FLC expression, resulting in earlier flowering.

Question 13

Which of the following best describes the function of general transcription factors (GTFs) in eukaryotic transcription?

Accepted Answer

They are required for all RNA polymerase II-mediated transcription and help form the preinitiation complex at the promoter.

Question 14

Which of the following is a correct statement about the role of TFIIH in eukaryotic transcription?

Accepted Answer

TFIIH acts as a protein kinase and DNA helicase, phosphorylating the CTD of RNA polymerase II and unwinding DNA.

Question 15

Which of the following is a posttranscriptional regulatory mechanism in eukaryotes?

Accepted Answer

Alternative splicing of pre-mRNA

Question 16

Which of the following best describes the relationship between chromatin structure and gene expression?

Accepted Answer

Relaxed euchromatin structure allows access to regulatory proteins and promotes gene expression.

Question 17

Which of the following is TRUE regarding the regulation of gene expression in eukaryotes?

Accepted Answer

Gene expression can be regulated at multiple levels, including transcription, mRNA processing, mRNA stability, translation, and posttranslational modification.

Question 18

Which of the following is a function of the TATA-binding protein (TBP) in eukaryotic transcription?

Accepted Answer

It determines the transcription start site by binding to the TATA box in the promoter region.

Question 19

Which of the following statements about regulatory (control) elements in eukaryotic gene expression is correct?

Accepted Answer

They are DNA sequences that serve as binding sites for transcription factors.

Gene Regulation in Prokaryotes and Eukaryotes: Mechanisms and Chromatin Structure

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