Question 1

During which phase of the cell cycle does DNA replication occur, and what is the primary purpose of this process?

Accepted Answer

DNA replication occurs during the S phase to produce identical sister chromatids for cell division.

Question 2

A scientist observes onion root tip cells under a microscope and notes condensed chromosomes aligned at the cell's equator. Which stage of mitosis is being observed?

Accepted Answer

Metaphase

Question 3

Which structure is responsible for separating sister chromatids during mitosis, and what is its mechanism of action?

Accepted Answer

The mitotic spindle, which attaches to kinetochores and pulls chromatids apart.

Question 4

If a cell fails to form a contractile ring during cytokinesis, what is the most likely outcome?

Accepted Answer

The cell will complete mitosis but remain as a single cell with two nuclei.

Question 5

Which of the following best describes the events of prophase in mitosis?

Accepted Answer

Chromosomes condense, the nuclear envelope breaks down, and spindle fibers begin to form.

Question 6

A cell is observed with chromosomes at opposite poles and a re-forming nuclear envelope. Which stage of mitosis is this?

Accepted Answer

Telophase

Question 7

Which equation best represents the number of chromosomes in a human cell after S phase but before mitosis?

Accepted Answer

$2n = 92$

Question 8

What is the primary function of the cleavage furrow during cytokinesis?

Accepted Answer

To divide the cytoplasm and physically separate the two daughter cells.

Question 9

Which of the following is NOT a correct description of sister chromatids?

Accepted Answer

They are different chromosomes inherited from each parent.

Question 10

A researcher stains cells and observes a contractile ring forming at the cell's equator. Which process is being observed, and what is the role of the contractile ring?

Accepted Answer

Cytokinesis; the contractile ring pinches the cell membrane to divide the cytoplasm.

Question 11

Which stage of the cell cycle is characterized by cell growth and preparation for DNA replication, but no DNA synthesis?

Accepted Answer

G$_1$ phase

Question 12

In a micrograph of a whitefish blastula, you observe cells with chromosomes being pulled toward opposite poles. Which mitotic stage is this?

Accepted Answer

Anaphase

Question 13

Which of the following events occurs during metaphase of mitosis?

Accepted Answer

Chromosomes align at the metaphase plate.

Question 14

A cell is observed in G$_2$ phase. Which of the following has already occurred?

Accepted Answer

DNA replication

Question 15

Which of the following best explains the role of the mitotic spindle during cell division?

Accepted Answer

It attaches to chromosomes and moves them to opposite poles.

Question 16

If a mutation prevents the formation of spindle fibers, which stage of mitosis would be directly affected and why?

Accepted Answer

Metaphase, because chromosomes cannot align at the metaphase plate.

Question 17

Which of the following is the correct sequence of mitosis stages?

Accepted Answer

Prophase, Metaphase, Anaphase, Telophase

Question 18

A cell in interphase is exposed to a DNA-damaging agent. Which checkpoint is most likely to halt the cell cycle to allow for repair?

Accepted Answer

G$_1$/S checkpoint

Question 19

Which event marks the transition from mitosis to cytokinesis?

Accepted Answer

Formation of the contractile ring and cleavage furrow

Question 20

In a clinical scenario, a patient’s cells are found to have abnormal numbers of chromosomes after cell division. Which mitotic event most likely failed?

Accepted Answer

Proper separation of sister chromatids during anaphase

Cell Cycle and Mitosis: Key Terms and Learning Objectives

Study Guide - Practice Questions

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