# data[].attributes.body
The website below goes in depth on the discovery of Mitosis

# data[].attributes.attachment_link.title
Discovery of Mitosis : HistoryofInformation.com

# data[].attributes.attachment_link.description
In 1878 German biologist and founder of cytogenetics Walther Flemming at the University of Kiel published the results of his investigations of the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread.

# data[].attributes.body
The following video shows the process of Mitosis

# data[].attributes.attachment_link.readable_text
Your browser does not support the video tag.
Mitosis

SOURCE: Sadava, et al., Life: The Science of Biology, Ninth Edition, published by Sinauer Associates. © 2010 Sinauer Associates and Sumanas, Inc. Life: The Science of Biology is available from Macmillan Learning.
KEYWORDS: Mitosis, chromosomes, independent assortment, prophase, metaphase, anaphase, telophase

# data[].attributes.attachment_link.description
Your browser does not support the video tag. Mitosis SOURCE: Sadava, et al., Life: The Science of Biology, Ninth Edition, published by Sinauer Associates. © 2010 Sinauer Associates and Sumanas, Inc. Life: The Science of Biology is available from Macmillan Learning. KEYWORDS: Mitosis, chromosomes, independent assortment, prophase, metaphase, anaphase, telophase

# data[].attributes.body
The following website talks more about cell division throughout the body

# data[].attributes.attachment_link.description
The other type of cell division, meiosis, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half-from 46 to 23-to form sperm and egg cells. When the sperm and egg cells unite at conception, each contributes 23 chromosomes so the resulting embryo will have the usual 46.

# data[].attributes.body
The following article describes what can go wrong during Mitosis

# data[].attributes.attachment_link.readable_text
Written by Stacy Taylor

The cells within living organisms have the ability to grow and reproduce through the production of new cells. In order to ensure that an exact copy of the DNA is assigned to the new cells, a process called mitosis takes place. When a new cell is needed, the DNA is copied and allocated equally to new cells; then the cell splits in half. While mitosis is a precise system for distributing DNA, it is very complex and includes many cell components that must work in concert. When any one of these intricate steps fails, the results can be adverse for the cell and the whole organism.

The Cell Cycle and Mitosis

In preparation for mitosis, cells become larger and copy their DNA. There are five steps to mitosis: prophase, prometaphase, metaphase, anaphase and telophase. These steps are defined by condensing of DNA into chromosomes, temporary removal of the nuclear membrane, separation of newly copied chromosomes, and moving separated chromosomes to opposite ends of the cell via spindle fibers. Nuclear membranes are then reformed around each cluster of separated chromosomes during telophase and the parent cell splits into two.

Changes in Chromosome Structure

Although relatively rare, damage can occur to chromosomes during mitotic movement. Sometimes a break occurs in a chromosome and a portion of it is lost, causing a deletion. If the broken fragment then reattaches upside down, this is called an inversion. Rarely, such fragments attach to a different chromosome, and lead to a translocation. Such errors in a growing embryo are primarily lethal, and lead to either miscarriages or still births. However, some do survive, born with serious birth defects. Cri du chat and Prader-Willi Syndrome are two disorders caused by chromosome deletion. Translocations or inversions can result in lymphomas, Down Syndrome, leukemias and some psychiatric disorders.

Changes in Chromosome Number

Nondisjunction is the result of failure of chromosomes to separate during mitosis. This leads to new cells with either extra or missing chromosomes; a condition called aneuploidy. Human embryos with aneuploidy rarely survive development; with only 0.3 percent of human aneuploidy pregnancies producing a live birth. For those children born with aneuploidy, severe genetic conditions result. The most common form of Down Syndrome, Turner syndrome, Edward's Syndrome, Patau Syndrome and Kleinfelter's Syndrome are a few aneuploidy disorders.

Mitotic Errors and Cancer

In essence, cancer is some form of uncontrolled cell growth. The usual checkpoints of the cell cycle do not work correctly, and cells progress and repeat mitosis when not needed. Researchers find many cancer cells with a variety of chromosome irregularities such as deletions, inversions and translocations. Such changes can alter control of the cell cycle. They can also activate genes known to be cancerous -- oncogenes. Changes may also inactivate tumor-suppressing genes. There is evidence of multiple types of cancers that exhibit aneuploidy in their cells.

About the Author

Stacy Taylor is an accomplished scientist, educator and writer. Taylor has a bachelor's degree in human biology, a master's degree in microbiology and additional graduate work in biomedicine and public health. Taylor has been teaching college biology courses since 1998.

Photo Credits

George Doyle/Stockbyte/Getty Images

# data[].attributes.attachment_link.description
The cells within living organisms have the ability to grow and reproduce through the production of new cells. In order to ensure that an exact copy of the DNA is assigned to the new cells, a process called mitosis takes place.

# data[].attributes.body
The website goes in depth about all the cell cycles

# data[].attributes.attachment_link.readable_text
The cell cycle

Living cells go through a series of stages known as the cell cycle. The cells grow, copy their chromosomes, and then divide to form new cells.

G1 phase. The cell grows.

S phase. The cell makes copies of its chromosomes. Each chromosome now consists of two sister chromatids.

G2 phase. The cell checks the duplicated chromosomes and gets ready to divide.

M phase. The cell separates the copied chromosomes to form two full sets (mitosis) and the cell divides into two new cells (cytokinesis).

The period between cell divisions is known as 'interphase'.

Cells that are not dividing leave the cell cycle and stay in G0.

Mitosis and meiosis

Cells divide into two different ways to make new cells.

Mitosis

Mitosis is used to produce daughter cells that are genetically identical to the parent cells. The cell copies - or 'replicates' - its chromosomes, and then splits the copied chromosomes equally to make sure that each daughter cell has a full set.

Meiosis

Meiosis is used to make special cells - sperm cells and egg cells - that have half the normal number of chromosomes. It reduces the number from 23 pairs of chromosomes to 23 single chromosomes. The cell copies its chromosomes, but then separates the 23 pairs to ensure that each daughter cell has only one copy of each chromosome. A second division that divides each daughter cell again to produce four daughter cells.

See below for more detailed descriptions of mitosis and meiosis.

Mitosis

Your body contains trillions of cells (thousands of millions). But you started life as a single cell - a fertilised egg cell. This cell then divided and divided to make more cells through a process called mitosis.

Mitosis is a way of making more cells that are genetically the same as the parent cell. It plays an important part in the development of embryos, and it is important for the growth and development of our bodies as well. Mitosis produces new cells, and replaces cells that are old, lost or damaged.

In mitosis a cell divides to form two identical daughter cells. It is important that the daughter cells have a copy of every chromosome, so the process involves copying the chromosomes first and then carefully separating the copies to give each new cell a full set.

Before mitosis, the chromosomes are copied. They then coil up, and each chromosome looks like a letter X in the nucleus of the cell. The chromosomes now consist of two sister chromatids. Mitosis separates these chromatids, so that each new cell has a copy of every chromosome.

A diagram of a cell ready for mitosis. The copied chromosomes consist of two chromatids joined at the centromere

The process of mitosis involves a number of different stages. The following diagram sets out the stages, and the main events that occur in each stage.

Meiosis

Some simple organisms - such as bacteria - can reproduce by simply dividing into two new individuals. Other organisms, including human beings, reproduce through sexual reproduction. New individuals are formed by the joining together of two special cells: a sperm cell and an egg cell.

The cells in our bodies contain 23 pairs of chromosomes - giving us 46 chromosomes in total. Sperm cells and egg cells contain 23 single chromosomes, half the normal number, and are made by a special form of cell division called meiosis.

Meiosis separates the pairs of matching (or 'homologous') chromosomes, so that sperm cells and egg cells have only one copy of each. That way, when an egg cell fuses with a sperm cell, the fertilised egg has a full set: that is, two copies of every chromosome.

Meiosis involves two cell divisions: Meiosis I and Meiosis II.

Meiosis I separates the matching - or 'homologous' - pairs of chromosomes.
Meiosis II divides each chromosome into two copies (much like mitosis).
In Meiosis I, each daughter cell receives a mix of chromosomes from the two sets in the parent cell. In addition, the chromosomes in each matching pair swap some genetic material before they are parted in a process called crossing over. These processes produce new combinations of genes in the sperm cells and egg cells.

The following diagrams set out the main stages of Meiosis I and Meiosis II in males. (A similar process in females produces egg cells rather than sperm cells.)

Back to top
This work is licensed under a Creative Commons Licence.

# data[].attributes.attachment_link.description
Living cells go through a series of stages known as the cell cycle. The cells grow, copy their chromosomes, and then divide to form new cells. G1 phase. The cell grows. S phase. The cell makes copies of its chromosomes. Each chromosome now consists of two sister chromatids. G2 phase.

# data[].attributes.body
This is what the process of Mitosis looks like