Mitosis is a highly controlled process in the cell cycle, where DNA and organelles of a cell are accurately divided into 2 identical daughter cells.
There are 4 main phases: prophase, metaphase, anaphase and telophase.
Quite a number of things happen during prophase.
- Chromatin (thread-like DNA) is supercoiled and condensed into chromosomes.
- The nuclear envelope breaks down, allowing the chromosomes to fill the entire cell space.
- The two centrosomes (or microtubule organizing centers, MTOCs) move apart to opposite ends of the cell.
- Microtubules polymerize from the centrosomes to form long mitotic spindles that can attach to the chromosomes to move them.
PROPHASE
The chromosomes are then moved by the mitotic spindle until they are all lined up in the middle of the cell, forming what is known as a metaphase plate. This stage of mitosis is called metaphase.
METAPHASE
The cell then proceeds to anaphase. The mitotic spindles shorten, separating the chromosome into two chromatids, and pulling each one to opposite ends of the cells.
ANAPHASE
At the end of mitosis (telophase) we have two identical sets of DNA at the poles of the cell. This DNA starts to decondense back to the thread-like chromatin structure. A nuclear envelope reassembles around each set, forming 2 nuclei.
TELOPHASE
After mitosis has completed, the cell then divides into 2 daughter cells, a stage known as cytokinesis. Read more about this final stage of the cell cycle.
Animations make it really easy to understand the different phases of mitosis. Here’s a really good one!
* All images here were modified from Molecular Biology of the Cell, 4th edition, Garland Science
