Question 1

Which of the following best explains why prokaryotic cells regulate gene expression primarily at the level of transcription?

Accepted Answer

Transcriptional control allows cells to conserve energy by only producing proteins when needed.

Question 2

A bacterial cell is growing in an environment with high tryptophan levels. Which of the following statements about the trp operon is correct?

Accepted Answer

Tryptophan acts as a corepressor, binds to the trp repressor, and the operon is turned off.

Question 3

Which of the following best describes the difference between negative and positive transcriptional control in prokaryotes?

Accepted Answer

Negative control involves repressors that block transcription, while positive control involves activators that enhance transcription.

Question 4

In the lac operon, what is the role of allolactose?

Accepted Answer

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

Question 5

A bacterial cell is placed in an environment with high lactose and low glucose. What will happen to the lac operon?

Accepted Answer

The operon will be highly transcribed because the repressor is inactive and CRP is activated by high cAMP.

Question 6

Which of the following scenarios would result in the lac operon NOT being transcribed?

Accepted Answer

Glucose is present and lactose is absent.

Question 7

Which statement about the structure and function of an operon in prokaryotes is correct?

Accepted Answer

An operon consists of a promoter, operator, and multiple genes transcribed as a single mRNA.

Question 8

Which of the following best describes the effect of histone acetylation on chromatin structure and gene expression in eukaryotes?

Accepted Answer

Histone acetylation loosens chromatin structure, making DNA more accessible for transcription.

Question 9

A mutation causes a eukaryotic cell to lack DNA methyltransferase activity. What is the most likely effect on gene expression?

Accepted Answer

Genes that are normally silenced by methylation may become abnormally active.

Question 10

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

Accepted Answer

Eukaryotic genes are often regulated by multiple enhancers located far from the promoter, while prokaryotic genes are typically regulated by operators near the promoter.

Question 11

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

Accepted Answer

An enhancer is a DNA sequence that can increase transcription rates when bound by specific activator proteins, even if located far from the gene.

Question 12

Which of the following is an example of epigenetic inheritance?

Accepted Answer

The pattern of DNA methylation is passed to daughter cells during mitosis, affecting gene expression without changing the DNA sequence.

Question 13

A researcher treats human cells with a drug that removes acetyl groups from histone tails. What is the most likely outcome?

Accepted Answer

Chromatin will become more condensed, and transcription of many genes will decrease.

Question 14

Which of the following best explains why the lac operon is regulated by both glucose and lactose concentrations?

Accepted Answer

Bacteria prefer to use glucose for energy, so the lac operon is only activated when glucose is low and lactose is available.

Question 15

Which of the following is true regarding the effect of DNA methylation on gene expression?

Accepted Answer

DNA methylation typically represses gene transcription.

Question 16

A cell needs to rapidly produce enzymes for a new metabolic pathway. Which gene regulatory mechanism would allow for the fastest response?

Accepted Answer

Transcriptional control via activator proteins binding to enhancers.

Question 17

Which of the following best describes how eukaryotic cells can coordinate the expression of multiple genes at once?

Accepted Answer

Multiple genes can share the same enhancer sequence, allowing them to be activated simultaneously by the same activator proteins.

Question 18

Which of the following is a correct statement about the operator in a prokaryotic operon?

Accepted Answer

The operator is a DNA sequence where a repressor protein can bind to block transcription.

Question 19

Which of the following scenarios would most likely lead to increased transcription of a gene in a eukaryotic cell?

Accepted Answer

Addition of acetyl groups to histone tails near the gene.

Gene Regulation in Prokaryotes and Eukaryotes: Study Guide

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