Question 1

Which of the following best describes the function of the operator in an operon?

Accepted Answer

It is a segment of DNA that acts as an on-off switch, controlling access of RNA polymerase to the genes.

Question 2

In the trp operon, what happens when tryptophan is present in high concentrations?

Accepted Answer

Tryptophan binds to the repressor, activating it, which then binds to the operator and blocks transcription.

Question 3

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

Accepted Answer

The lac repressor is inactivated by allolactose, allowing transcription of the operon.

Question 4

Which of the following best explains why identical twins can have different susceptibilities to genetically based diseases?

Accepted Answer

Epigenetic inheritance can cause differences in gene expression without altering the DNA sequence.

Question 5

Which chemical modification of histones is most likely to increase gene expression?

Accepted Answer

Histone acetylation

Question 6

A mutation in the p53 gene is most likely to result in which of the following outcomes?

Accepted Answer

Failure to suppress the cell cycle, leading to increased risk of cancer

Question 7

Which of the following mechanisms allows a single gene to code for multiple proteins in eukaryotes?

Accepted Answer

Alternative RNA splicing

Question 8

What is the role of microRNAs (miRNAs) in gene regulation?

Accepted Answer

They bind to complementary mRNA sequences, causing degradation or blocking translation.

Question 9

Which of the following best describes the difference between a repressible and an inducible operon?

Accepted Answer

A repressible operon is usually on and can be turned off by a corepressor, while an inducible operon is usually off and can be turned on by an inducer.

Question 10

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

Accepted Answer

Long-term inactivation of genes during cellular differentiation

Question 11

A scientist discovers a mutation that prevents the addition of ubiquitin to proteins in a cell. What is the most likely consequence?

Accepted Answer

Proteins will accumulate because they are not targeted for degradation by proteasomes.

Question 12

Which of the following statements about enhancers is correct?

Accepted Answer

Enhancers are distal control elements that can be far from the gene they regulate.

Question 13

Which of the following best explains why eukaryotic mRNA is generally more stable than prokaryotic mRNA?

Accepted Answer

Eukaryotic mRNA is protected by a 5' cap and a poly-A tail, and its stability is influenced by sequences in the 3' UTR.

Question 14

Which of the following scenarios illustrates feedback inhibition?

Accepted Answer

The end product of a metabolic pathway inhibits the activity of an enzyme earlier in the pathway.

Question 15

Which of the following is a function of tumor-suppressor genes?

Accepted Answer

Repair damaged DNA and inhibit the cell cycle

Question 16

A mutation in the ras proto-oncogene leads to a hyperactive Ras protein. What is the most likely cellular outcome?

Accepted Answer

Increased cell division due to constant signaling in the absence of growth factors

Question 17

Which of the following best describes the process of alternative RNA splicing?

Accepted Answer

The production of different mRNA molecules from the same primary transcript by varying which segments are treated as exons and introns

Question 18

Which of the following is an example of epigenetic inheritance?

Accepted Answer

The transmission of gene expression patterns caused by DNA methylation, not changes in DNA sequence

Question 19

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

Accepted Answer

Loosening of chromatin structure, making DNA more accessible for transcription

Question 20

A cell is exposed to a signal that activates translation initiation factors for all mRNAs. What is the most likely result?

Accepted Answer

Translation of all mRNAs in the cell increases simultaneously.

Regulation of Gene Expression (Chapter 18): Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards