How Does Mitosis Work in the Cell Cycle?

Mitosis is the stage of the cell cycle in which one set of chromosomes is pulled to each end of a cell and the nucleus divides. The cell then divides to produce two genetically identical daughter cells.

The three stages of the cell cycle

1. Growth and DNA replication

Before the cell divides, it grows and increases the number of sub-cellular structures, such as mitochondria and ribosomes.

The cell's DNA is then replicated. This means that an identical copy of each chromosome is made, so there is enough genetic material for both new cells.

2. Mitosis

During mitosis, one copy of each chromosome is pulled to each end of the cell. The nucleus then divides.

This ensures that each new nucleus contains the same genetic information and the same number of chromosomes as the original body cell.

3. Division of the cell

Finally, the cytoplasm and cell membrane divide. This produces two genetically identical daughter cells.

Why is mitosis important?

Mitosis produces new cells for:

• growth and development of multicellular organisms
• repairing damaged tissues
• replacing old or damaged cells

In mature animals, cell division is mainly used for repair and replacement.

Worked example

A skin cell needs to divide to replace a damaged cell. It first grows and copies its DNA. During mitosis, the copied chromosomes are separated into two nuclei. The cytoplasm and cell membrane then divide, producing two genetically identical skin cells.

Common exam mistake

Do not describe the whole cell cycle as mitosis. Mitosis only refers to the division of the nucleus. DNA replication happens before mitosis, while division of the cytoplasm and cell membrane happens afterwards.

For AQA GCSE Biology, you need to understand these three overall stages, but you do not need to learn the individual phases within mitosis.

Scope assumed: Higher tier and separate GCSE Biology. This content is also required at Foundation tier and is shared with Combined Science.