Question 1

Which of the following best explains the adaptive advantage of grouping genes into an operon in bacteria?

Accepted Answer

It allows for the coordinated regulation of genes with related functions, enabling efficient response to environmental changes.

Question 2

In the trp operon, what is the role of the corepressor?

Accepted Answer

The corepressor (tryptophan) binds to the repressor protein, activating it so it can bind to the operator and block transcription.

Question 3

Which of the following statements about the lac operon is correct?

Accepted Answer

Allolactose acts as an inducer by binding to the repressor, causing it to release from the operator and allowing transcription.

Question 4

Which of the following best distinguishes repressible enzymes from inducible enzymes?

Accepted Answer

Repressible enzymes are usually part of anabolic pathways and are inhibited by their end product, while inducible enzymes are part of catabolic pathways and are activated by the substrate.

Question 5

Which scenario represents positive control of the lac operon?

Accepted Answer

cAMP binds to CRP, and the cAMP-CRP complex enhances transcription of the lac operon when glucose is scarce.

Question 6

How does glucose concentration affect cAMP levels and the activity of the lac operon?

Accepted Answer

Low glucose increases cAMP, which binds to CRP and enhances lac operon transcription.

Question 7

Which of the following best defines differential gene expression in eukaryotes?

Accepted Answer

The expression of different genes by cells with the same genome, leading to cell specialization.

Question 8

Which of the following modifications would most likely increase transcription of a eukaryotic gene?

Accepted Answer

Histone acetylation, which loosens chromatin structure and promotes transcription.

Question 9

Which statement about epigenetic inheritance is correct?

Accepted Answer

It involves the transmission of gene expression patterns without changes to the DNA sequence.

Question 10

Which of the following is NOT a level at which gene expression can be regulated in eukaryotic cells?

Accepted Answer

Replication of DNA

Question 11

A mutation prevents the addition of a 5' cap to pre-mRNA in a eukaryotic cell. What is the most likely consequence?

Accepted Answer

The mRNA will be rapidly degraded and not efficiently translated.

Question 12

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

Accepted Answer

They are noncoding DNA sequences that serve as binding sites for transcription factors, influencing the rate of transcription.

Question 13

Which combination of factors is required for the initiation of transcription in eukaryotes?

Accepted Answer

General transcription factors, RNA polymerase, and promoter DNA sequence

Question 14

How can eukaryotic cells coordinately express a group of genes with related functions, such as those needed for a metabolic pathway?

Accepted Answer

By having the same combination of control elements in the regulatory regions of each gene, allowing the same transcription factors to activate them simultaneously.

Question 15

Alternative RNA splicing allows eukaryotic cells to:

Accepted Answer

Produce different proteins from the same gene by including or excluding certain exons.

Question 16

Which of the following statements about mRNA longevity is correct?

Accepted Answer

mRNA molecules in eukaryotes generally last longer than those in prokaryotes, allowing for more prolonged protein synthesis.

Question 17

A scientist discovers a eukaryotic gene that is highly methylated and not expressed. What is the most likely explanation?

Accepted Answer

DNA methylation condenses chromatin, making the gene inaccessible to transcription machinery.

Question 18

Which of the following is an example of post-translational control of gene expression?

Accepted Answer

Phosphorylation of a protein, altering its activity after translation.

Question 19

A patient is diagnosed with a genetic disorder caused by a mutation that prevents the removal of introns from pre-mRNA. What is the most likely consequence?

Accepted Answer

The resulting mRNA will contain noncoding sequences, leading to a nonfunctional protein.

Question 20

Which of the following best describes the role of enhancers in eukaryotic gene regulation?

Accepted Answer

Enhancers are distant DNA elements that increase the rate of transcription when bound by specific activator proteins.

Regulation of Gene Expression: Bacterial and Eukaryotic Mechanisms

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