$$\text{Lactose} + \text{H}_2\text{O} \xrightarrow{\beta\text{-Galactosidase}} \text{Glucose} + \text{Galactose}$$

Question 1

Which of the following best describes the mechanism of feedback inhibition in the tryptophan biosynthetic pathway, as shown in the first image?

Accepted Answer

Tryptophan binds to the first enzyme in the pathway, reducing its activity and thus decreasing tryptophan synthesis.

Question 2

In prokaryotic gene regulation, what is the primary function of the operator region in an operon?

Accepted Answer

It serves as the binding site for regulatory proteins that control transcription.

Question 3

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

Accepted Answer

The trp operon is a repressible operon that is turned off when tryptophan binds to the repressor.

Question 4

Referencing the lac operon, which molecule acts as the inducer to inactivate the repressor and allow transcription?

Accepted Answer

Allolactose

Question 5

Which equation correctly represents the enzymatic breakdown of lactose by β-galactosidase?

Accepted Answer

$$	ext{Lactose} + 	ext{H}_2	ext{O} \xrightarrow{\beta	ext{-Galactosidase}} 	ext{Glucose} + 	ext{Galactose}$$

Question 6

What happens to the lac operon when both glucose and lactose are absent?

Accepted Answer

The operon is not transcribed because the repressor remains bound to the operator.

Question 7

Which of the following best explains why histone acetylation increases transcription in eukaryotic cells?

Accepted Answer

Acetylation opens chromatin structure, allowing transcription factors to access DNA.

Question 8

Which of the following is a consequence of DNA methylation in eukaryotic cells?

Accepted Answer

Decreased transcription due to condensed chromatin structure.

Question 9

Epigenetic inheritance refers to:

Accepted Answer

Inheritance of gene expression patterns without changes to the DNA sequence.

Question 10

Which of the following statements about microRNAs (miRNAs) is correct?

Accepted Answer

miRNAs are single-stranded RNAs that bind to complementary mRNA sequences and inhibit translation.

Question 11

Which of the following mutations would most likely convert a proto-oncogene into an oncogene?

Accepted Answer

A mutation that greatly increases the amount of the proto-oncogene protein.

Question 12

Which of the following best describes the function of tumor-suppressor genes?

Accepted Answer

They encode proteins that help prevent uncontrolled cell growth.

Question 13

Which of the following would be most likely to lead to cancer?

Accepted Answer

Amplification of a proto-oncogene and inactivation of a tumor-suppressor gene.

Question 14

Why do cells possess proto-oncogenes, which have the potential to become cancer-causing genes?

Accepted Answer

Proto-oncogenes are necessary for the normal control of cell growth and division.

Question 15

Which of the following is a stage at which eukaryotic gene expression can be regulated?

Accepted Answer

At multiple levels, including chromatin modification, transcription, RNA processing, translation, and protein degradation.

Question 16

Alternative RNA splicing allows eukaryotic cells to:

Accepted Answer

Produce different proteins from the same DNA template.

Question 17

Which of the following best describes the effect of histone methylation?

Accepted Answer

Histone methylation decreases transcription by condensing chromatin.

Question 18

Which of the following is a real-world example of epigenetic inheritance?

Accepted Answer

A woman who smokes while pregnant induces epigenetic changes in herself, her unborn daughter, and her daughter's reproductive cells.

Question 19

Which of the following best explains why eukaryotes do not have operons?

Accepted Answer

Eukaryotes use control elements and specific transcription factors to regulate genes located on different chromosomes.

Regulation of Gene Expression: Prokaryotic and Eukaryotic Mechanisms

Study Guide - Practice Questions