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, and how does it affect gene expression?

Accepted Answer

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

Question 3

Which of the following scenarios best illustrates negative control of gene expression in the lac operon?

Accepted Answer

The lac repressor binds to the operator, preventing transcription in the absence of lactose.

Question 4

How does the presence of glucose affect the levels of cyclic AMP (cAMP) and the activity of the cAMP receptor protein (CRP) in E. coli?

Accepted Answer

High glucose leads to low cAMP, reducing CRP activation and decreasing transcription of the lac operon.

Question 5

Which of the following best distinguishes between repressible and inducible operons?

Accepted Answer

Repressible operons are usually on and can be turned off by a corepressor, while inducible operons are usually off and can be turned on by an inducer.

Question 6

Which of the following is an example of positive control of gene expression in the lac operon?

Accepted Answer

cAMP-CRP complex binding to the promoter, increasing the affinity of RNA polymerase for the lac operon.

Question 7

Which of the following best defines differential gene expression in eukaryotic cells?

Accepted Answer

The expression of different genes by cells with the same genome.

Question 8

Which of the following modifications to chromatin structure is most likely to increase transcription of a gene?

Accepted Answer

Histone acetylation, which loosens chromatin structure and promotes transcription.

Question 9

Which of the following statements about epigenetic inheritance is correct?

Accepted Answer

It involves the transmission of heritable changes in gene expression that do not involve changes to the DNA sequence.

Question 10

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 11

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

Accepted Answer

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

Question 12

Which of the following is a key difference between general and specific transcription factors in eukaryotes?

Accepted Answer

General transcription factors are required for the transcription of all protein-coding genes, while specific transcription factors regulate particular genes.

Question 13

Which of the following best explains how eukaryotic genes can be coordinately expressed, even if they are located on different chromosomes?

Accepted Answer

They share common control elements that allow the same transcription factors to activate their expression simultaneously.

Question 14

Alternative RNA splicing allows eukaryotic cells to:

Accepted Answer

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

Question 15

Which of the following factors is most likely to increase the life span of mRNA in the cytoplasm of a eukaryotic cell?

Accepted Answer

The presence of a long poly-A tail at the 3' end of the mRNA.

Question 16

Which of the following statements correctly compares the longevity of mRNA in prokaryotes and eukaryotes?

Accepted Answer

mRNA is generally more stable and lasts longer in eukaryotes than in prokaryotes.

Question 17

A scientist discovers a mutation that prevents the acetylation of histone proteins in a eukaryotic cell. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease because chromatin will remain more condensed.

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 abnormal DNA methylation patterns. Which of the following best explains how this could lead to disease?

Accepted Answer

Abnormal methylation can silence tumor suppressor genes, leading to uncontrolled cell growth.

Regulation of Gene Expression: Prokaryotic and Eukaryotic Mechanisms

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