Question 1

Which of the following best describes an operon in prokaryotic gene regulation?

Accepted Answer

A cluster of genes regulated as a unit, along with their promoter sequence

Question 2

In the lac operon, what happens when both glucose and lactose are present in the environment?

Accepted Answer

Transcription of lac genes is low because glucose inhibits cAMP production

Question 3

Which molecule acts as an inducer in the lac operon system?

Accepted Answer

Allolactose

Question 4

What is the role of the repressor protein in the trp operon?

Accepted Answer

It binds to the operator to block RNA polymerase when tryptophan is present

Question 5

Which of the following equations correctly represents the relationship between cAMP and glucose concentration in E. coli?

Accepted Answer

$$[\mathrm{cAMP}] \propto \frac{1}{[\mathrm{Glucose}]}$$

Question 6

A mutation causes the operator region of the lac operon to be unable to bind the repressor. What is the most likely outcome?

Accepted Answer

The lac genes will be transcribed continuously, even in the absence of lactose

Question 7

Which of the following best explains why bacteria prefer lactose to glucose, according to the study materials?

Accepted Answer

This statement is false; bacteria prefer glucose to lactose because glucose is a more efficient energy source

Question 8

Which chromatin modification is associated with increased transcriptional activity?

Accepted Answer

Histone acetylation

Question 9

What is the effect of DNA methylation on gene expression?

Accepted Answer

It generally represses gene transcription

Question 10

Which of the following is TRUE regarding epigenetic inheritance?

Accepted Answer

Epigenetic changes such as DNA methylation can be passed to offspring and affect gene expression

Question 11

Which of the following best describes combinatorial control of gene expression?

Accepted Answer

Gene expression depends on the combination of multiple transcription factors binding to regulatory regions

Question 12

A cell has high levels of acetylated histones and low levels of DNA methylation. What is the expected effect on gene expression?

Accepted Answer

Increased transcriptional activity

Question 13

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

Accepted Answer

It is repressible and is turned off when tryptophan is present

Question 14

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

Accepted Answer

Loosening of chromatin structure, allowing transcription factors to access DNA

Question 15

If a bacterial cell is grown in a medium containing only lactose (no glucose), what will happen to the lac operon?

Accepted Answer

The lac operon will be highly transcribed due to high cAMP and CRP activation

Question 16

Which of the following best explains the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is densely packed and transcriptionally inactive

Question 17

Which of the following is a key step in cell differentiation according to the study materials?

Accepted Answer

Selective activation and repression of genes by transcription factors

Question 18

A scientist observes that a gene is only expressed when both activator A and activator B are present. Which concept does this illustrate?

Accepted Answer

Combinatorial control of gene expression

Question 19

Which of the following statements about gene regulation in eukaryotes is TRUE?

Accepted Answer

Gene regulation can occur at multiple stages, including chromatin modification, transcription, and post-transcriptional processing

Question 20

Which of the following is a plausible consequence of a mutation that prevents DNA methylation in a cell?

Accepted Answer

Increased expression of genes that are normally silenced

Regulation of Gene Expression (Chapter 15) – Study Notes

Study Guide - Practice Questions