Question 1

Which of the following best explains why skeletal muscle cells, neurons, and skin cells (as shown in the first image) have different structures and functions, even though they contain the same DNA?

Accepted Answer

They express different sets of genes due to gene regulation.

Question 2

Based on the diagram comparing bacterial and eukaryotic gene regulation, which of the following is a unique feature of eukaryotic gene regulation?

Accepted Answer

Regulation at the level of RNA modification (pre-mRNA processing).

Question 3

A small effector molecule binds to a repressor protein, causing it to change shape and release from the DNA. What is the most likely result?

Accepted Answer

Transcription of the gene will increase.

Question 4

Which of the following sequences is most likely to be found approximately 25 base pairs upstream of a eukaryotic gene's transcriptional start site and is essential for the formation of the core promoter?

Accepted Answer

$$5'	ext{–TATAAAA–}3'$$

Question 5

What is the role of general transcription factors (GTFs) in eukaryotic transcription initiation, as shown in the preinitiation complex image?

Accepted Answer

They help RNA polymerase II bind to the promoter and initiate transcription.

Question 6

In the context of the mediator complex and enhancer interaction, what is the primary function of the mediator in eukaryotic transcription?

Accepted Answer

It mediates interactions between transcription factors and RNA polymerase II, controlling the rate of transcription initiation.

Question 7

Which of the following best describes the effect of histone acetyltransferase (HAT) activity on chromatin structure and gene expression?

Accepted Answer

HATs add acetyl groups to histones, leading to chromatin decondensation and increased gene expression.

Question 8

A mutation in the CpG island near a tumor-suppressor gene promoter leads to abnormal methylation. What is the most likely consequence?

Accepted Answer

Transcription of the tumor-suppressor gene will be inhibited, increasing cancer risk.

Question 9

Alternative splicing of pre-mRNA allows a single gene to:

Accepted Answer

Produce multiple different polypeptides with specialized functions.

Question 10

Which type of mutation is most likely to result in a truncated (shortened) polypeptide?

Accepted Answer

Nonsense mutation

Question 11

A patient is exposed to UV light, which causes the formation of thymine dimers in their DNA. Which DNA repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair (NER)

Question 12

A mutation occurs in a somatic cell during early development. Which of the following best describes the likely outcome?

Accepted Answer

A patch of tissue in the organism will carry the mutation, but it will not be passed to offspring.

Question 13

Which of the following is a common effect of a missense mutation in the coding region of a gene?

Accepted Answer

A single amino acid in the polypeptide is changed.

Question 14

Which of the following mutagens acts by inserting itself between DNA bases and distorting the double helix, potentially causing additions or deletions?

Accepted Answer

Benzo(a)pyrene

Question 15

A proto-oncogene can become an oncogene by all of the following mechanisms EXCEPT:

Accepted Answer

Silent mutation in the coding region

Question 16

The Ras protein is involved in cell signaling. What is the effect of an oncogenic mutation that decreases Ras's ability to hydrolyze GTP?

Accepted Answer

Ras remains active, continuously promoting cell division.

Question 17

Which of the following best describes the 'two-hit' model for retinoblastoma development?

Accepted Answer

Both copies of the Rb gene must be inactivated for the disease to develop.

Question 18

Which of the following is NOT a typical function of tumor-suppressor genes?

Accepted Answer

Promoting cell division in response to growth factors

Question 19

A cell is found to have extra copies of a chromosome containing a proto-oncogene. What is the most likely effect?

Accepted Answer

Overexpression of the proto-oncogene, increasing cancer risk.

Chapter 14

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