Question 1

Which of the following best describes the difference between homologous chromosomes and sister chromatids, as shown in the first image?

Accepted Answer

Homologous chromosomes are a pair of chromosomes, one from each parent, while sister chromatids are identical copies formed by DNA replication of a single chromosome.

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the result in terms of chromosome structure?

Accepted Answer

DNA replication occurs during the S phase, resulting in each chromosome consisting of two sister chromatids.

Question 3

Refer to the cell cycle diagram (third image). Which phase is the longest, and what is its primary function?

Accepted Answer

Interphase; it is responsible for cell growth, DNA replication, and preparation for mitosis.

Question 4

Which checkpoint in the cell cycle (fourth image) is primarily responsible for ensuring that DNA is undamaged before replication begins?

Accepted Answer

G1 checkpoint

Question 5

A mutation in the ras gene leads to a Ras protein that is always active (see images 5 and 6). What is the most likely cellular outcome?

Accepted Answer

The cell will continuously divide, even in the absence of growth factors.

Question 6

What is the role of the p53 protein in the cell cycle, as shown in images 7 and 8?

Accepted Answer

p53 inhibits the cell cycle in response to DNA damage, allowing time for repair or triggering apoptosis.

Question 7

If both copies of the p53 gene are mutated in a cell, what is the most likely consequence?

Accepted Answer

The cell will be unable to inhibit the cell cycle in response to DNA damage, leading to increased risk of cancer.

Question 8

Which of the following best explains how Herceptin works as a therapy for HER2-positive breast cancer (see images 9 and 10)?

Accepted Answer

Herceptin binds to the HER2 receptor, blocking its activity and preventing excessive cell division.

Question 9

A chemotherapy drug that disrupts microtubule formation would most directly interfere with which stage of mitosis?

Accepted Answer

Metaphase

Question 10

Which of the following equations correctly represents the change in DNA content during the S phase of the cell cycle?

Accepted Answer

$$2n \rightarrow 4n$$

Question 11

A patient is treated with doxorubicin, which intercalates into DNA and inhibits DNA synthesis. During which phase of the cell cycle would this drug have its maximum effect?

Accepted Answer

S phase

Question 12

Which of the following best describes the function of actin filaments during cell division?

Accepted Answer

Actin filaments form the contractile ring that pinches the cell during cytokinesis.

Question 13

If a cell is exposed to a drug that causes the disassembly of actin filaments, what is the most likely effect on cell division?

Accepted Answer

The cell will be unable to complete cytokinesis.

Question 14

Which of the following statements about proto-oncogenes and tumor suppressor genes is correct?

Accepted Answer

A mutation in only one copy of a proto-oncogene can lead to cancer.

Question 15

Which of the following best explains why environmental chemicals can lead to cancer?

Accepted Answer

They can cause mutations in DNA, leading to the activation of oncogenes or inactivation of tumor suppressor genes.

Question 16

A cell with a defective p53 protein is exposed to UV light. What is the most likely outcome?

Accepted Answer

The cell will be unable to inhibit the cell cycle, leading to increased risk of cancer.

Question 17

Which of the following best describes the role of the centromere during mitosis?

Accepted Answer

The centromere is the region where sister chromatids are joined and where spindle fibers attach.

Question 18

Which of the following is a direct result of a nonfunctional spindle checkpoint during mitosis?

Accepted Answer

Cells may undergo aneuploidy due to improper chromosome segregation.

Question 19

Which of the following best describes the function of the HER2 receptor in breast cancer cells?

Accepted Answer

HER2 is a growth factor receptor that, when overexpressed, leads to increased cell division.

Cell Division, Cancer, and Chemotherapy: Step-by-Step Study Guidance

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