Mitosis and Stem Cells

This page provides an in-depth look at the process of mitosis and introduces the concept of stem cells.

Definition: Mitosis is a type of cell division that produces genetically identical cells, also known as clones.

The guide presents a step-by-step breakdown of mitosis, from DNA replication during interphase to the final cytokinesis stage:

1. DNA replication during interphase
2. Chromosome condensation and alignment
3. Separation of sister chromatids
4. Cell division resulting in two identical daughter cells

Highlight: The end result of mitosis is two daughter cells that are genetically identical and diploid.

The role of spindle fibers in chromosome separation is explained, emphasizing their importance in ensuring accurate distribution of genetic material.

Vocabulary: Spindle fibers are special structures that pull chromosomes to opposite ends of the cell during mitosis.

The concept of stem cells is introduced, with a focus on their unique properties:

Definition: A stem cell is an undifferentiated cell capable of giving rise to many more cells of the same type and from which certain other specialized cells can arise through differentiation.

The guide touches on the development from gametes to zygote to embryo, introducing the term "blastocyst" and explaining the concept of totipotency.

Vocabulary: Totipotency refers to a cell's ability to differentiate into all specialized cell types.

This comprehensive overview of mitosis and stem cells provides students with a solid foundation for understanding cell division and differentiation in the context of GCSE Biology.

The Cell Cycle and DNA Replication

This section delves into the intricate process of the cell cycle, focusing on the stages of interphase and mitosis.

Definition: The cell cycle is the series of events that takes place in a cell leading to its division and duplication.

The interphase stage is broken down into three sub-phases:

1. G1 (Gap 1): Cell growth and preparation for DNA synthesis
2. S (Synthesis): DNA replication occurs
3. G2 (Gap 2): Further cell growth and preparation for mitosis

Highlight: During the S phase, each of the 46 chromosomes is duplicated, resulting in 92 chromatids.

The guide also mentions the G0 (Zero Growth) phase, where cells exit the cycle after specialization.

Vocabulary: Cytokinesis is the process where the cytoplasm and cell membranes divide to form two identical daughter cells.

The importance of mitosis in various biological processes is emphasized:

• Growth from a zygote to an adult
• Repair and replacement of damaged cells
• Asexual reproduction in some organisms

Example: In plants, mitosis is crucial for asexual reproduction, allowing new individuals to grow from a single parent cell.

The page concludes with a detailed diagram of the cell cycle, illustrating the relationship between interphase, mitosis, and cytokinesis.