What Is Cell Division and Why Does It Matter?
Every living organism is made of cells — the basic units of life. But where do new cells come from? The answer is simple: cells come from pre-existing cells through a process called cell division.
The process by which a parent cell divides into two or more daughter cells, passing on genetic information to the next generation of cells.
Cell division is one of the most fundamental processes in biology. Without it, you could not grow, heal a wound, or replace worn-out cells. Your body performs millions of cell divisions every single second!
There are two main types of cell division in eukaryotes (organisms with a nucleus):
- Mitosis — produces two genetically identical daughter cells; used for growth, repair, and asexual reproduction
- Meiosis — produces four genetically unique daughter cells; used for sexual reproduction (covered in a separate subtopic)
In this subtopic, we focus entirely on mitosis.
Think of cell division like photocopying a document. Mitosis makes perfect, identical copies of the original — every copy has exactly the same information as the original page.
MYP Key Concept — Change: Mitosis is a perfect example of the key concept of Change. Through cell division, living organisms undergo transformation at the cellular level — enabling growth, development, and renewal throughout life. As you work through this subtopic, think about how change at the microscopic scale of a single cell drives visible change in whole organisms.
The Cell Cycle: Life of a Cell
Before a cell can divide, it must go through a series of carefully controlled stages known as the cell cycle.
The ordered sequence of events a cell undergoes from its formation to its own division into two daughter cells.
The cell cycle has two major phases:
- Interphase — the long preparation phase where the cell grows and copies its DNA
- Mitotic Phase (M Phase) — the actual division of the nucleus (mitosis) followed by division of the cytoplasm (cytokinesis)
Interphase is further divided into three sub-stages:
| Sub-stage | What Happens |
|---|---|
| G₁ (Gap 1) | Cell grows larger; proteins and organelles are produced |
| S (Synthesis) | DNA is replicated — every chromosome is copied |
| G₂ (Gap 2) | Cell continues growing; checks that DNA replication was accurate |
Interphase is NOT a resting stage — it is an extremely active period. The cell is preparing everything it needs to divide successfully. A cell spends about 90% of its life in interphase.
The cell cycle also has built-in checkpoints — quality-control moments at key points (for example, at the end of G₁ and G₂) where the cell checks whether conditions are right to proceed. These checkpoints are crucial: if they are damaged by mutations, the result can be uncontrolled cell division. You will read more about this in the cancer section.
(!image: Diagram showing the cell cycle as a circle divided into interphase — with G₁, S, and G₂ sub-stages labelled — and the mitotic phase (M), with relative time proportions indicated. Checkpoints should be marked at the G₁/S and G₂/M boundaries.)
13 more sections in this topic
Pick this up in your Library: it holds the whole topic, notes, cheatsheet and questions.