Question 1

Which of the following best describes the function of the trp operon in E. coli when tryptophan is present in the environment?

Accepted Answer

Tryptophan binds to the repressor, activating it, and the complex binds to the operator to repress transcription.

Question 2

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

Accepted Answer

In eukaryotes, gene regulation occurs at multiple levels, including chromatin remodeling and mRNA processing.

Question 3

How does histone acetylation generally affect gene expression in eukaryotes?

Accepted Answer

It decreases the positive charge on histones, loosening DNA binding and promoting transcription.

Question 4

A mutation in the TATA box of a core promoter would most likely result in which of the following?

Accepted Answer

Reduced or abolished transcription initiation due to impaired pre-initiation complex formation.

Question 5

Which of the following statements about enhancers is correct?

Accepted Answer

Enhancers can function at a distance from the gene, even within introns, and increase transcription rates.

Question 6

Which enzyme is responsible for removing acetyl groups from histone tails, leading to chromatin condensation and gene repression?

Accepted Answer

Histone deacetylase (HDAC)

Question 7

DNA methylation most commonly occurs at which nucleotide sequence in eukaryotic genomes?

Accepted Answer

CpG islands

Question 8

A researcher finds that a mutation prevents the binding of the glucocorticoid receptor to the GRE (glucocorticoid response element) in the MT2A gene promoter. What is the most likely consequence?

Accepted Answer

MT2A transcription will not be induced by glucocorticoids during stress.

Question 9

Which of the following best explains why alternative splicing is important in eukaryotic gene regulation?

Accepted Answer

It allows a single gene to encode multiple protein isoforms with potentially different functions.

Question 10

In the context of the trp operon, what is the role of the leader sequence containing the attenuator?

Accepted Answer

It acts as a regulatory site that can terminate transcription prematurely under certain conditions.

Question 11

Which of the following is a function of the pre-initiation complex (PIC) in eukaryotic transcription?

Accepted Answer

It mediates the unwinding of promoter DNA and the transition of RNA polymerase from initiation to elongation.

Question 12

A mutation that prevents the removal of ubiquitin from a protein would most likely result in which cellular outcome?

Accepted Answer

The protein would be targeted for degradation by the proteasome.

Question 13

Which of the following best describes the function of silencers in eukaryotic gene regulation?

Accepted Answer

They act as negative regulators, repressing transcription in a tissue- or temporal-specific manner.

Question 14

Which of the following is true regarding focused and dispersed core promoters?

Accepted Answer

Dispersed promoters are used by most higher eukaryotes and direct transcription from several weak start sites.

Question 15

Which of the following is a direct effect of histone acetyltransferase (HAT) activity?

Accepted Answer

Addition of acetyl groups to histone tails, promoting transcription.

Question 16

A patient has a mutation that causes constitutive expression of a gene normally regulated by a silencer. Which of the following is the most likely explanation?

Accepted Answer

The silencer element or its binding protein is nonfunctional, preventing repression.

Question 17

Which of the following best describes the recruitment model of transcription regulation in eukaryotes?

Accepted Answer

DNA looping brings activators and general transcription factors to the promoter, increasing PIC assembly.

Question 18

Which of the following is a consequence of chromatin being in a 'closed' conformation?

Accepted Answer

DNA replication, repair, and transcription are inhibited.

Question 19

Which of the following is NOT a core-promoter element found in focused promoters?

Accepted Answer

CAAT box

Regulation of Gene Expression: The trp Operon and Eukaryotic Mechanisms

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