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Topic 1 - Life at the Molecular, Cellular and Tissue Level

Focus: Cell Division - Mitosis

• Pages: 86-97

• Source: Understanding Life Sciences Grade 10, Third Edition

• Compiled by: Marike Elisna Röth

Lesson Outline

1. Introduction

2. Recap on the Nucleus

   • Importance and structure of the nucleus

3. Chromosomes

   • Structure and function

4. Importance of Mitosis

   • Growth, repair, and reproduction

5. Cell Cycle

   • Growth and division of the cell

   • Interphase

   • Phases of Mitosis:

     • Prophase

     • Metaphase

     • Anaphase

     • Telophase

6. Cancer

   • Definition and role in cell division

7. Practical Investigation of Mitosis

   • Experimentation methods

Introduction to Mitosis

• Focus on the division of cells, specifically somatic cells through mitosis.

• Two types of cells in the human body:

  1. Somatic Cells - Resulting from mitosis

  2. Sex Cells/Gametes - Resulting from meiosis

• In Grade 10, focus is on mitosis; meiosis is covered in Grade 12.

Recap on the Nucleus

• Components of the Nucleus:

  • Endoplasmic Reticulum, Nucleolus, Chromatin, Nucleoplasm, Nuclear Pore, Nuclear Envelope, Ribosome

• Functions of the Nucleus:

  1. Control of all cell activities

  2. Control of enzyme production

  3. Enclosure/protection of chromatin

  4. Carrying hereditary information through chromosomes

• Chromatin Network: Tangled threads that condense into chromosomes during division.

Life Cycle of Cells

• Both humans and cells have life cycles.

• Interphase: Cell growth and DNA replication occur.

• Dividing Phase (Mitosis): Division of the nucleus and cytoplasm occurs.

Dividing Phases

Definitions

• Karyokinesis: Division of the nucleus and chromosomes

• Cytokinesis: Division of the cytoplasm and organelles

• Two types of division:

  1. Mitosis - Diploid (2n)

  2. Meiosis - Haploid (n)

Importance of Mitosis

• Mitosis is crucial for:

  1. Growth of an organism

  2. Repair and replacement of damaged tissues

  3. Asexual reproduction in certain organisms

  • Mitosis results in two identical daughter cells with the same chromosome number as the parent cell.

Problems of Cell Size

• As cells grow, nutrient transport and waste removal become inefficient.

• A solution to maintain homeostasis is cell division.

• Mitosis occurs in:

  • Plants: Apical and lateral meristem

  • Animals: Bone marrow and skin

Phases of Mitosis

1. Prophase

   • Chromatin condenses into visible chromosomes

2. Metaphase

   • Chromosomes align at the equator of the cell

3. Anaphase

   • Chromatids separate and move to opposite poles

4. Telophase

   • Daughter cells begin forming as nuclei develop

Sites of Mitosis

Animal vs. Plant Cells

• Animal Cells: Centrosome forms spindle fibers

• Plant Cells: Do not have centrosomes; formation of a cell plate during cytokinesis

Cancer Overview

• Cancer arises from uncontrolled mitotic cell division.

• Tumors can be:

  1. Benign: Encapsulated, does not invade surrounding tissues

  2. Malignant: Spreads and damages surrounding tissues

• Carcinogenic agents can lead to cancer formation.

Cancer Treatment Options

1. Radiotherapy: Use of radioactive radiation

2. Chemotherapy: Use of chemical agents

3. Surgery: Removal of tumors, though risk of regrowth exists

Practical Investigation of Mitosis

Method: Onion Root Tip Experiment

1. Grow roots in water and dark

2. Cut root tips and process with dyes

3. Observe under a microscope for various stages of mitosis

4. Draw and label observed stages

Summary and Final Notes

• Mitosis is essential for growth and tissue repair.

• Understanding phases of mitosis helps in identifying and addressing issues such as cancer.