$$\text{DNA} \xrightarrow{\text{transcription}} \text{mRNA} \xrightarrow{\text{translation}} \text{Protein}$$

Question 1

Which of the following best describes the role of the operator in the lac operon of E. coli?

Accepted Answer

It acts as a switch that determines whether the RNA polymerase can attach to the promoter and transcribe the genes.

Question 2

In the absence of lactose, what happens to the lac operon in E. coli?

Accepted Answer

The repressor binds to the operator, preventing transcription of the lactose-metabolizing genes.

Question 3

Which statement about cell differentiation in humans is correct?

Accepted Answer

All cells contain the same set of genes, but only certain genes are expressed depending on cell type.

Question 4

Why is DNA packaging by histone proteins important for eukaryotic cells?

Accepted Answer

It enables the large amount of DNA to fit into the small nucleus and helps regulate gene expression.

Question 5

A female cat is heterozygous for an X-linked gene controlling fur color. What is the expected result of X chromosome inactivation?

Accepted Answer

Some cells will express the allele from the mother, and others from the father, leading to a mosaic phenotype.

Question 6

Which of the following is TRUE regarding the trp operon in E. coli?

Accepted Answer

The trp operon repressor is inactive when tryptophan is absent, allowing transcription.

Question 7

Which equation best represents the relationship between gene expression and protein production?

Accepted Answer

$$	ext{DNA} \xrightarrow{	ext{transcription}} 	ext{mRNA} \xrightarrow{	ext{translation}} 	ext{Protein}$$

Question 8

Which of the following statements about alternative mRNA splicing is correct?

Accepted Answer

It allows a single gene to produce multiple different proteins by varying the combination of exons included in the final mRNA.

Question 9

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

Accepted Answer

Prokaryotes use operons to regulate groups of related genes, while eukaryotes typically regulate each gene individually with its own promoter.

Question 10

What is the function of activator proteins in eukaryotic transcription?

Accepted Answer

They bind to enhancers and help recruit transcription factors and RNA polymerase to the promoter, facilitating transcription.

Question 11

A mutation causes the lac repressor protein to be unable to bind lactose. What is the most likely consequence for E. coli?

Accepted Answer

The lac operon will remain off even when lactose is present, preventing the digestion of lactose.

Question 12

Which of the following best explains why only one X chromosome is active in each female cell?

Accepted Answer

To ensure equal protein production from X-linked genes in males and females.

Question 13

Which process is most directly responsible for the removal of introns from pre-mRNA in eukaryotic cells?

Accepted Answer

Alternative RNA splicing

Question 14

Housekeeping genes are typically:

Accepted Answer

Continually expressed in all metabolically active cells.

Question 15

Which of the following is TRUE about the packaging of DNA in eukaryotic cells?

Accepted Answer

Histone proteins help organize DNA into nucleosomes, which are further coiled into supercoils.

Question 16

Which of the following scenarios best illustrates the concept of gene regulation in response to environmental changes?

Accepted Answer

E. coli turns on the lac operon only when lactose is present in the environment.

Question 17

Which of the following is a consequence of random X chromosome inactivation in female mammals?

Accepted Answer

Mosaic expression of X-linked traits, such as the tortoiseshell pattern in cats.

Question 18

Which of the following is NOT a function of transcription factors in eukaryotic cells?

Accepted Answer

Directly splicing introns from mRNA.

Question 19

If a mutation caused the operator sequence in the lac operon to be deleted, what would be the most likely effect?

Accepted Answer

The lac operon would be constitutively expressed, as the repressor could not bind to block transcription.

Gene Expression and Control: Mechanisms and Regulation

Study Guide - Practice Questions