Mitosis | Biology for GCSE/IGCSE - Year 11 PDF Download

New Cells are Made by Mitosis

Mitosis - Basics

• Most body cells possess a pair of each chromosome, referred to as diploid cells.
• Before cell division, chromosomes replicate, ensuring that the resulting daughter cells also contain a complete set of chromosomes.
• Diploid cells maintain genetic stability by preserving the chromosome count during cell division.
• Mitosis is crucial for various biological processes such as growth, repairing damaged tissues, replacing old cells, and asexual reproduction.
• Mitosis refers to the division of the cell nucleus, resulting in the production of genetically identical daughter cells.

Process

The process of cell division by mitosis involves the following steps:

• Just before mitosis, each chromosome in the nucleus copies itself exactly, forming X-shaped chromosomes.
• Chromosomes line up along the center of the cell, where cell fibers pull them apart.
• The cell divides into two, and each new cell contains a copy of each of the chromosomes.

Importance

• All cells in the body (excluding gametes) are produced by mitosis of the zygote.
• Mitosis is essential for replacing cells, such as skin cells and red blood cells, and for enabling growth, for instance, the production of new cells when a zygote divides to form an embryo.

Occurs in

• Growth: Mitosis is a crucial process for the growth of living organisms as it continually produces new cells.
• Repair: Damaged or dead cells in the body are replaced through the process of mitosis, ensuring proper functioning of tissues and organs.
• Asexual Reproduction: In some organisms, mitosis is responsible for asexual reproduction, where offspring are exact genetic copies of the parent.

Mitosis & Stem Cells: In-Depth Explanation

• Presence of Stem Cells in Human Tissues: Various tissues in the human body contain a limited number of unspecialized cells known as stem cells.
• Function of Stem Cells: Stem cells have the unique ability to divide through mitosis, generating new daughter cells that can specialize and undertake specific functions within the tissue.
• Role of Zygote: The zygote represents the fundamental stem cell, dividing multiple times via mitosis to form a cluster of unspecialized cells, termed embryonic stem cells.
• Embryonic Stem Cells Development: These embryonic stem cells, initially identical, gradually differentiate as the fetus matures, acquiring distinct characteristics and purposes.

Mitosis and Embryonic Stem Cells

• When a zygote undergoes multiple divisions through mitosis, it transforms into a cluster of undifferentiated cells, typically comprising 200 to 300 cells. These cells are recognized as embryonic stem cells.
• Embryonic stem cells are initially identical and commence the process of specialization as the embryo matures, acquiring distinct characteristics.
• As embryonic stem cells progress in development, they evolve into various cell types, each serving a unique purpose in the growing fetus.