Question 1

Which of the following best describes the role of histones in the structure of eukaryotic chromosomes?

Accepted Answer

Histones are proteins that coil and compact DNA into nucleosomes, aiding chromosome condensation.

Question 2

During which phase of the cell cycle does DNA replication occur, and what is the result for each chromosome?

Accepted Answer

DNA replication occurs during S phase, resulting in chromosomes composed of two sister chromatids joined at the centromere.

Question 3

A scientist observes a cell with condensed chromosomes aligned at the center of the cell, spindle fibers attached to kinetochores, and no nuclear envelope. Which phase of mitosis is this cell in?

Accepted Answer

Metaphase

Question 4

Which checkpoint in the cell cycle is primarily responsible for ensuring that the cell’s DNA is undamaged and that the cell is ready to commit to division?

Accepted Answer

G₁ checkpoint

Question 5

What is the main difference between cytokinesis in plant cells and animal cells?

Accepted Answer

Animal cells form a cleavage furrow using a contractile ring of actin and myosin, while plant cells form a cell plate from vesicles that fuse to create a new cell wall.

Question 6

Which of the following best explains why cancer cells can form tumors?

Accepted Answer

Cancer cells ignore cell-cycle checkpoints, leading to uncontrolled division and loss of contact inhibition.

Question 7

A mutation in the p53 gene would most likely result in which of the following cellular outcomes?

Accepted Answer

Cells would fail to undergo apoptosis in response to DNA damage, increasing cancer risk.

Question 8

Which of the following events occurs during anaphase of mitosis?

Accepted Answer

Sister chromatids are pulled apart toward opposite poles of the cell.

Question 9

Why do cells enter the G₀ phase, and what is a real-life example of a cell type that commonly resides in G₀?

Accepted Answer

Cells enter G₀ when they no longer divide but perform specialized functions; neurons are an example.

Question 10

Which of the following best describes the relationship between cyclins and cyclin-dependent kinases (Cdks) in cell cycle regulation?

Accepted Answer

Cyclins bind to Cdks, activating them to phosphorylate target proteins and drive cell cycle progression.

Question 11

A patient’s skin cells are exposed to a growth factor after an injury. Which of the following best describes the cellular response?

Accepted Answer

Cells receive the signal, re-enter the cell cycle, and divide to repair the tissue.

Question 12

Which of the following is a correct sequence of events during the M phase of the cell cycle?

Accepted Answer

Prophase → Prometaphase → Metaphase → Anaphase → Telophase

Question 13

Which of the following statements about telomeres is correct?

Accepted Answer

Telomeres shorten with each cell division, eventually leading to cell senescence or apoptosis.

Question 14

Which of the following best explains why the M checkpoint is critical for proper cell division?

Accepted Answer

It ensures that all chromosomes are properly attached to spindle fibers before anaphase, preventing unequal chromosome distribution.

Question 15

Which of the following is a property of malignant tumors but not benign tumors?

Accepted Answer

They invade nearby tissues and can metastasize to distant sites.

Question 16

A researcher observes a eukaryotic cell with uncoiled chromatin, active gene expression, and organelle duplication. In which phase of the cell cycle is this cell most likely found?

Accepted Answer

Interphase (G₁ or G₂)

Question 17

Which of the following equations correctly represents the chromosome number changes during mitosis in a human cell (2n = 46)?

Accepted Answer

$$46 \rightarrow 92 \rightarrow 46$$

Question 18

Which of the following best describes the difference between chromatin and a chromosome?

Accepted Answer

Chromatin is uncoiled DNA and proteins for gene expression and replication, while a chromosome is condensed DNA and proteins for segregation during cell division.

Question 19

Which of the following scenarios would most likely result in apoptosis?

Accepted Answer

A cell with irreparable DNA damage detected at the G₁ checkpoint.

The Eukaryotic Cell Cycle and Mitosis: Structure, Regulation, and Clinical Relevance

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