Question 1

Which of the following best explains how two cells with identical genomes can have different structures and functions?

Accepted Answer

They express different sets of genes due to differential gene expression.

Question 2

In the trp operon of E. coli, what is the role of tryptophan?

Accepted Answer

It acts as a corepressor, activating the repressor to shut off the operon.

Question 3

Which of the following scenarios would result in maximal transcription of the lac operon in E. coli?

Accepted Answer

Glucose absent, lactose present

Question 4

Which statement correctly distinguishes between repressible and inducible operons?

Accepted Answer

Repressible operons are usually on and can be turned off by a corepressor, while inducible operons are usually off and can be turned on by an inducer.

Question 5

Which of the following best describes the effect of histone acetylation on gene expression?

Accepted Answer

It opens chromatin structure, promoting transcription initiation.

Question 6

A mutation in the regulatory gene of the lac operon results in a repressor protein that cannot bind allolactose. What is the most likely outcome?

Accepted Answer

The lac operon will never be transcribed, even if lactose is present.

Question 7

Which of the following is an example of epigenetic inheritance?

Accepted Answer

Methylation of DNA that silences a gene without changing the DNA sequence.

Question 8

Which mechanism allows a single gene to code for multiple proteins in eukaryotes?

Accepted Answer

Alternative RNA splicing

Question 9

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

Accepted Answer

They degrade or block translation of target mRNAs.

Question 10

A researcher introduces a mutation that prevents the p53 protein from binding DNA. What is a likely consequence in the cell?

Accepted Answer

The cell will be unable to initiate apoptosis in response to DNA damage.

Question 11

Which of the following best describes the role of activator proteins in eukaryotic transcription?

Accepted Answer

They bind to enhancers and increase the rate of transcription.

Question 12

In the context of cancer, what is the difference between a proto-oncogene and an oncogene?

Accepted Answer

A proto-oncogene is a normal gene that can become an oncogene through mutation, leading to uncontrolled cell division.

Question 13

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

Accepted Answer

Long-term inactivation of the methylated gene

Question 14

A fruit fly embryo whose mother lacks a functional bicoid gene will most likely develop with which abnormality?

Accepted Answer

It will lack anterior structures and have posterior structures at both ends.

Question 15

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

Accepted Answer

They repair damaged DNA, control cell adhesion, and inhibit the cell cycle.

Question 16

Which of the following is a likely outcome if a mutation causes the Ras protein to be constitutively active?

Accepted Answer

The cell will undergo uncontrolled division, increasing cancer risk.

Question 17

Which of the following is true about the regulation of gene expression in eukaryotes compared to prokaryotes?

Accepted Answer

Eukaryotic gene expression is regulated at multiple levels, including chromatin structure, transcription, and RNA processing.

Question 18

Which of the following best describes the role of cytoplasmic determinants in embryonic development?

Accepted Answer

They are maternal substances unevenly distributed in the egg that influence early gene expression.

Question 19

Which of the following is a real-world application of RNA interference (RNAi) using siRNAs?

Accepted Answer

Disabling specific genes to study their function in the laboratory

Question 20

Which of the following best explains why elephants have a lower cancer rate compared to humans?

Accepted Answer

They have more copies of the p53 gene, enhancing their ability to suppress tumors.

Regulation of Gene Expression (Chapter 18, Campbell Biology)

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