Cell Division: Mitosis

Understanding the process of cell division and its importance in growth, repair, and reproduction

CAPS Grade 10 Life Sciences

In this topic, learners need to know the cell cycle, the stages of mitosis, and why mitosis is important. You should also be able to explain how uncontrolled mitosis can lead to cancer.

1. The Cell Cycle

Mitosis is a critical component of the cell cycle, which encompasses the entire life of a cell. The cell cycle consists of three main phases:

Interphase

This is the longest phase of the cell cycle, during which the cell grows, performs its normal functions, and prepares for division by replicating its DNA.

G1 (Gap 1): Cell growth and normal functions

S (Synthesis): DNA replication

G2 (Gap 2): Preparation for mitosis

Mitosis (M Phase)

This phase involves the actual division of the nucleus, where the replicated chromosomes are separated into two new nuclei.

PMAT: Prophase, Metaphase, Anaphase, Telophase

Cytokinesis

Following mitosis, cytokinesis is the process that divides the cytoplasm of the parent cell, resulting in two distinct daughter cells.

In animal cells: cleavage furrow forms
In plant cells: cell plate forms

Interphase (G1, S, G2) Mitosis Cytokinesis Cell

Figure 1: The Cell Cycle - Interphase (longest), Mitosis, and Cytokinesis

Quick Check: Cell Cycle

1. What are the three main phases of the cell cycle?

Show Answer

Interphase, Mitosis, and Cytokinesis.

2. What happens during the S phase of interphase?

Show Answer

DNA synthesis (replication) occurs during the S phase.

3. Which phase of the cell cycle is the longest?

Show Answer

Interphase is the longest phase of the cell cycle.

2. The Phases of Mitosis (PMAT)

Mitosis can be broken down into four distinct phases, often abbreviated as PMAT. It is essential to identify, draw, and describe the changes that occur to the chromosomes during each phase:

P
Prophase

During prophase, chromatin condenses into visible chromosomes, each consisting of two sister chromatids. The nuclear membrane begins to disintegrate, and spindle fibers start to form from the centrosomes.

M
Metaphase

In metaphase, the chromosomes align in a single row along the equatorial plane of the cell. Spindle fibers attach to the centromeres of the chromosomes.

A
Anaphase

Anaphase is characterized by the separation of sister chromatids, which are pulled apart by the spindle fibers and move toward opposite ends of the cell.

T
Telophase

In telophase, new nuclear membranes form around each set of daughter chromosomes, which begin to de-condense back into chromatin. The cell membrane starts to constrict.

PMAT Mnemonic Helper

P

Prophase

Mnemonic: "P" for "Prepare"

Chromosomes condense and become visible. Nuclear membrane breaks down.

M

Metaphase

Mnemonic: "M" for "Middle"

Chromosomes line up in the middle of the cell.

A

Anaphase

Mnemonic: "A" for "Apart"

Sister chromatids are pulled apart to opposite poles.

T

Telophase

Mnemonic: "T" for "Two"

Two new nuclei begin to form.

Arrange the Phases of Mitosis

Sequencing Game
Score: 0/4
Phase 1
Phase 2
Phase 3
Phase 4
Prophase

Chromosomes condense

Metaphase

Line up in middle

Anaphase

Pull apart

Telophase

Two nuclei form

Click a phase card, then click the correct slot (1-4) to place it in order.

3. The Significance of Mitosis

Mitosis is important because it increases cell numbers while keeping the chromosome number the same. In Grade 10 questions, this usually links to growth, tissue repair, and asexual reproduction.

Growth

Mitosis is essential for increasing the number of cells in multicellular organisms, allowing for growth and development from a single fertilized egg into a complex organism.

Repair

Mitosis facilitates the replacement of damaged or worn-out tissues, such as during the healing of cuts, injuries, or replacement of skin cells and blood cells.

Asexual Reproduction

In certain organisms, such as Amoeba, bacteria, or plants that reproduce through cuttings, mitosis is utilized to produce offspring without fertilization.

Significance of Mitosis Quiz

1. Which process allows a cut on your skin to heal?

2. How does an Amoeba reproduce?

3. Which of the following is NOT a function of mitosis?

4. Cancer: Uncontrolled Mitosis

Understanding the consequences of a breakdown in the cell cycle is crucial, particularly in the context of cancer:

Definition of Cancer

Cancer is defined as a disease resulting from uncontrolled cell division, leading to the formation of a mass of cells known as a tumor.

Types of Tumors

Benign Tumors Non-cancerous

These are non-cancerous growths that do not spread to surrounding tissues. They grow slowly and are usually not life-threatening unless they press on vital organs.

  • Do not invade nearby tissues
  • Do not spread to other parts of the body
  • Can often be removed by surgery

Malignant Tumors Cancerous

These are cancerous and have the potential to invade and destroy surrounding tissues, a process known as metastasis.

  • Invade and destroy nearby tissues
  • Can spread through blood or lymph system
  • Form secondary tumors (metastasis)

Causes of Cancer (Carcinogens)

Several factors can lead to cancer, including exposure to carcinogens:

Radiation (UV rays, X-rays)
Chemicals (cigarette smoke)
Viruses (HPV, hepatitis B)

Cancer Quiz

1. What is the main difference between benign and malignant tumors?

2. What is metastasis?

3. Which of the following is an example of a chemical carcinogen?

Exam Tip

In examinations, you will likely encounter diagrams depicting cells in various stages of mitosis. You may be asked to identify the phase or arrange the stages in the correct order. Pay close attention to the positioning of the chromosomes: if they are aligned in the middle of the cell, you are observing metaphase; if they are being pulled apart, you are in anaphase. Also remember PMAT: Prophase, Metaphase, Anaphase, Telophase.

Comprehensive Practice Quiz

1. What are the three main phases of the cell cycle?

2. During which phase do chromosomes line up in the middle of the cell?

3. Which of the following is a function of mitosis?

1. What happens during the S phase of interphase?

1. What is the correct order of mitosis phases?

1. Which process uses mitosis to create offspring without fertilization?

1. Which type of tumor is cancerous and can spread to other parts of the body?

Fill in the Blanks

1. The cell cycle consists of interphase, mitosis, and .

2. During , chromosomes line up in the middle of the cell.

3. Cancer is caused by cell division.

4. The spread of cancer to other parts of the body is called .

5. The correct order of mitosis phases is PMAT: Prophase, Metaphase, , Telophase.

Key Terms

Cell cycle Interphase Mitosis Cytokinesis Prophase Metaphase Anaphase Telophase PMAT Chromosome Chromatid Centromere Spindle fibers Growth Repair Asexual reproduction Cancer Tumor Benign Malignant Metastasis Carcinogen

Summary

Mitosis is a critical process of cell division that occurs in three main phases of the cell cycle: interphase (growth and DNA replication), mitosis (nuclear division), and cytokinesis (cytoplasmic division). Mitosis itself consists of four phases (PMAT): Prophase (chromosomes condense), Metaphase (chromosomes align), Anaphase (sister chromatids separate), and Telophase (new nuclei form). Mitosis is essential for growth, repair of tissues, and asexual reproduction in some organisms. When mitosis becomes uncontrolled, it can lead to cancer - the formation of tumors. Malignant tumors are cancerous and can spread through metastasis, while benign tumors are non-cancerous and do not spread.