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Cell division

3  of  10

Mitosis in action

Nuclear division is an ordered process that results in the formation of two new cells with identical nuclei containing identical sets of chromosomechromosome
A chromosome is like a packet of coiled up DNA. Humans have 23 pairs of chromosomes. They are in the nucleus of every human cell.
s. Once mitosis starts it is a continuous process this can be seen by running the animation below without pauses. However to make it easier to understand, we usually describe it in stages.

Prophase: The pairs of chromosomechromosome
A chromosome is like a packet of coiled up DNA. Humans have 23 pairs of chromosomes. They are in the nucleus of every human cell.
s have replicated and become visible. Each chromosome is a pair of chromatidschromatids
Copies of the original chromosomes involved in mitosis and meiosis.
 joined at the centromerecentromere
Region that connects the pairs of chromatids in the early stages of mitosis and meiosis.
. The nucleolusnucleolus
Dense region of DNA and protein found in the nucleus of the cell.
 breaks down. The centriolescentrioles
Paired structures found in eukaryotic cells that produce a spindle of microtubules during mitotic and meiotic cell division. This spindle is key for correct chromosome segregation.
 begin to separate, forming a spindle of microtubules between them.

Metaphase: The nuclear membranenuclear membrane
The thin, flexible structure enclosing the contents of the nucleus in a cell.
 begins to break down. The centrioles move to opposite poles of the cell and a spindle of microtubules stretches between them. The chromatids jostle and move to line up along the centre of the spindle (the equator or metaphase plate), each chromatid is attached to the spindle fibre by the centromere.

Anaphase: The centromeres between the chromatids separate. The proteins of the spindle fibres contract and the chromatids are pulled along the spindle fibres towards the opposite poles of the cell, with the centromeres leading.

Telophase: In early telophase the chromatids reach the poles of the cell and are now known as chromosomes again. New nuclear membranes start to form around each group of chromosomes. Nucleoli form in the new nuclei, and centrioles reform in both cells. The division of the cytoplasm begins, leading to cytokinesiscytokinesis
The process by which the cytoplasm, cell surface membranes and cell walls divide to make daughter cells after mitotic or meiotic division of the nuclei.
.

Mitosis Main Stage (1)
Cell Onion Mitosis

Microscopic images of onion root tip squash showing stages of mitosis.

(Photo credit: staticd. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license)

Cytokinesiscytokinesis
The process by which the cytoplasm, cell surface membranes and cell walls divide to make daughter cells after mitotic or meiotic division of the nuclei.

The final stage of cell divisioncell division
The process by which a parent cell divides into two daughter cells.
is the splitting of the cytoplasm along with all the organellesorganelles
A distinct part of the cell, such as the nucleus, ribosome or mitochondrion, which has structure and function.
it contains. The cell surface membranemembrane
A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism.
 has to reform around each of the new cells. In plant cells, new cellulosecellulose
A complex carbohydrate which makes up plant cell walls.
cell walls also have to form and so the process is rather more complicated.

In animal cells

a ring of contractile protein fibres tighten around the middle of the cell like a belt, until the two halves are separated. The cell membranemembrane
A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism.
is flexible and seals around the two halves.

In plant cells

the cell wall builds up from the centre of the cell. Some of the spindle fibre remains left in the cytoplasm seem to guide Golgi vesiclesGolgi vesicles
Membrane bounded vesicles produced by the Golgi apparatus of the cell, also known as the Golgi body. These vesicles contain proteins, often enzymes.
 to line up in the middle of the large single cell with two nuclei. They form vacuoles that extend and fuse with the surface cell membranemembrane
A thin, flexible sheet-like structure that acts as a lining or a boundary in an organism.
s, separating the contents of the two new cells. Cellulosecellulose
A complex carbohydrate which makes up plant cell walls.
plates are then laid down and fuse to form a complete cell wall, completing the two new cells.

Cyto Animal