Mitosis (Cambridge IGCSE Biology): Revision notes

Section 1

What Happens During Mitosis?

Before nuclear division can occur, the exact replication of chromosomes takes place, so each chromosome consists of two identical copies joined together.

Mitosis is nuclear division that gives rise to two genetically identical daughter cells. During mitosis, the copies of each chromosome separate, one copy going to each new nucleus — this maintains the same chromosome number in each daughter cell as in the parent cell.

For reference: a diploid nucleus contains two sets of chromosomes; a haploid nucleus contains a single set. Mitosis keeps a cell's diploid number unchanged from one generation of cells to the next.

Key termsmitosisdiploidhaploid

Common mistake

Don't confuse mitosis (identical cells, same chromosome number) with meiosis (genetically different cells, chromosome number halved) — they serve different purposes.

Section 2

Why Is Mitosis Important?

Mitosis has several essential roles in an organism:

Growth: increasing the total number of cells in an organism as it develops
Repair of damaged tissues: replacing cells that have been injured
Replacement of cells: renewing cells that naturally wear out, such as skin cells or blood cells
Asexual reproduction: producing genetically identical offspring from a single parent

Example

When you cut your skin, mitosis produces new, genetically identical skin cells to repair the wound.

Section 3

What Are Stem Cells and How Are They Related to Mitosis?

Stem cells are unspecialised cells that divide by mitosis to produce daughter cells that can then become specialised for particular functions — for example becoming a muscle cell, a nerve cell, or a blood cell. Stem cells therefore provide the source of new cells needed for growth and for repairing tissue.

Key termsstem cell

Must Know

Chromosomes are exactly replicated before mitosis takes place
Mitosis produces two genetically identical daughter cells
The chromosome number is maintained (not halved) in mitosis
Mitosis is needed for growth, repair of damaged tissue, replacement of cells, and asexual reproduction
Stem cells are unspecialised cells that divide by mitosis and can become specialised

That's the notes covered.

Carry on to the next subtopic.